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Hybrid Electric Vehicles (HEVs) are a prominent solution for reducing CO2 emissions from transport in Europe. They are equipped with at least two propulsion energy converters, an Internal Combustion Engine (ICE) and one or more Electric Machines (EMs), operated in a way to exploit synergies and achieve fuel efficiency. Because of the variety in configurations and strategies, the use of simulation is essential for vehicle development and characterisation of energy consumption. This paper introduces a novel simulation approach to estimate the CO2 emissions from different hybrid architectures (series, parallel, power-split) and electrification degrees (mild, full, plug-in and range extender) that is relatively simple, flexible and accurate. The approach identifies the optimal power split between the energy converters for any given time in a driving cycle according to three evaluation levels: supervisor, ICE manager and optimiser. The latter relies on the Equivalent Consumption Minimisation Strategy (ECMS) and the limitations imposed by the other two layers. Six light-duty HEVs with different hybrid architectures were tested to support the development of the approach. The results show an indicative accuracy of ±5%, enabling to run assessments of hybrid powertrain solutions and supporting regulatory and consumer information initiatives. [ABSTRACT FROM AUTHOR]

A vehicle simulation model, CO 2 MPAS supports the introduction of the new WLTP-based certification system for CO 2 emissions in Europe. This paper investigates the possibility to use the underlying simulation methodology to accurately calculate CO 2 emissions over real-world trips, thus to extend the use of the methodology beyond vehicle certification. As a reference, the analysis used measurement data obtained from four vehicles over two different routes under real-world driving conditions. The CO 2 emissions were measured using portable emissions measurement systems. The formal CO 2 MPAS methodology and two modified versions of it that require a reduced number of input data were assessed about their capacity to predict the measured CO 2 emissions. The analysis focused on the accuracy and uncertainty of the three different methodology configurations. As an additional benchmark, the analysis considered the CO 2 emissions estimates obtained from the EMEP/EEA Guidebook methodology used for emissions inventorying in Europe. Results show that the basic CO 2 MPAS configuration demonstrates good performance in predicting CO 2 emissions over on-road tests, reaching a prediction accuracy over an entire test trip of −0,3% and a standard deviation of 3,1%. The modified versions showed slightly higher biases up to 3% and uncertainties (5–7%), but remaining within reasonable limits considering the reduced number of inputs used in each case. Given its ability to predict CO 2 emissions accurately on a local base, CO 2 MPAS could be used for the prediction of instantaneous CO 2 emissions in traffic micro-simulation exercises. [ABSTRACT FROM AUTHOR]

Abstract Despite that Heavy-Duty Vehicles (HDVs) represent a small part of the overall vehicle population they have been identified as one of the most important contributors to air pollution. This is one of the reasons why HDV emissions regulations are becoming more and more stringent worldwide. Following this trend, Europe introduced the Euro VI standard which includes more stringent emission limits for hydrocarbons, PM and NO x , while for the first time a limit for solid PN emissions was set. At the same time increased concern regarding greenhouse gas emissions led to a series of initiatives including HDVs CO 2 certification and monitoring with the latest being the submission of a proposal for CO 2 emission targets for 2025 and 2030. Despite the general concern, published data regarding Euro VI HDV emissions are scarce, while real-world emission factor measurements of regulated and unregulated pollutants are even more difficult to find. The main objective of this paper is to present real-world diesel Euro VI HDVs emissions of both gaseous pollutants and solid PN. For that reason five HDVs, including four trucks and one bus, were tested on-road under typical driving conditions. A breakdown of the emissions to low, medium, and high speed conditions was also performed with the aim investigating the performance of aftertreatment systems under different speed conditions. All tested vehicles performed better compared to older technology diesel HDVs, thus reflecting the technological improvements introduced over the last years. However, relatively high emissions were observed for some of the pollutants over low speed phases due to reduced effectiveness of the corresponding emission control systems. Calculated emission factors were also compared to existing emission inventories and good correlation was found for NO x , CO 2 and solid PN emissions. Highlights • Five Euro VI HDVs were tested on-road under typical driving conditions. • The vehicles demonstrated overall lower emissions compared to older technology HDVs. • Relatively high emissions were observed for some pollutants over low speed phases. • Emission inventories succeed in calculating real world EFs of Euro VI HDVs. [ABSTRACT FROM AUTHOR]

Abstract CO 2 emissions of light-duty vehicles are certified over standardised, laboratory-based conditions and reported to the consumers. Such tests reflect specific operating conditions that differ from what an individual driver experiences. Vehicle simulation can bridge the gap and help provide customised, vehicle and trip-specific values. This study investigates the potential of using a simulation-based approach for calculating CO 2 emissions over real-world operation, when limited information and test-data are available. The methodology introduced in the European vehicle certification regulation since 2017 is used as a basis. Seven vehicles were tested over multiple on-road trips and in some cases on a chassis dyno. First, the analysis focused on the accuracy of the simulations when only limited information for the vehicle and its components are used. Subsequently, the model was calibrated on test data. The first case presented an error between 1.0% and 4.4% depending on the test, while the standard deviation was 10.0%. When using WLTP for calibration, the average error dropped to −2.9% to −0.2%, and the standard deviation decreased to 2.0%. When calibrating over on-road tests, the average error was 0.7% for the on-road tests and 4.5% for the WLTP. Highlights • A simulation-based method for estimating lab and real world CO 2 of LDVs is investigated. • 3 different approaches were investigated based on generic, real world or lab input data. • The average error remained low (<5%) and was <2% when calibrating on tests-data. • Test-data based calibration significantly reduces the uncertainty from 10% to about 3%. • The approach could serve for extrapolating certification data to real world or vice versa. [ABSTRACT FROM AUTHOR]

As of July 2017, the emissions type-approval of light-duty vehicles in Europe is based on the Worldwide Harmonized Light-duty vehicles Test Procedure (WLTP), introduced to replace the old and outdated New European Driving Cycle (NEDC) test procedure. Since some elements of the European Legislation are still based on the NEDC (2020 CO 2 emission targets, vehicle labelling, national vehicle taxation policies, etc.) in order to allow sufficient lead time to vehicle manufacturers and national authorities to adapt to the new procedure, a simulation-based approach was chosen to calculate CO 2 emissions and fuel consumption according to the NEDC regime in the period 2017–2020. To achieve this objective without significantly increasing the cost and duration of the certification procedure, existing regulation foresees that vehicles are tested over the WLTP for CO 2 emissions, the test results are used as input in a simulation model that then calculates the corresponding CO 2 according to the NEDC test protocol. A dedicated vehicle simulation model (CO 2 MPAS) was developed for the purpose and is currently used for the type-approval of new vehicles in Europe. The development specifications of CO 2 MPAS were challenging, as it had to be highly accurate, exhibit fast operation, and function with a limited number of input data. This paper presents the development principles and process followed, details of the physical models employed in CO 2 MPAS, and provides information regarding its accuracy, validity and in use operation. CO 2 MPAS achieves low errors in the prediction of the NEDC cycle that in the controlled sample used for its development are of the order of 1% with a standard deviation of 3%, while the respective in-use numbers are of the order of 1.5% and 5%. In parallel, random sampling and testing of a 10% of the type-approved vehicles also occurs in order to guarantee the quality of the CO 2 MPAS results and the validity of the process. It is concluded that CO 2 MPAS can be used to accurately estimate emissions of conventional vehicles within a ±4% accuracy range, even when limited input data are available. In addition, the in-use data analyzed suggest that the use of the tool enables the certification of about 2/3 of the new vehicle models without the need of additional experimental tests. This is an important achievement as it reduces the costs and time necessary to certify light-duty vehicle CO 2 emissions during the transitional period. Finally, it can be concluded that the use of CO 2 MPAS does not affect the declared CO 2 emissions of vehicles over NEDC conditions. [ABSTRACT FROM AUTHOR]

Common approaches to assess the evolution of CO 2 emissions from road vehicles are usually based on (a) estimates of future fleet composition, where most approaches consider vehicles at a rather aggregated level, and (b) emission factors, which are either based on CO 2 certification data or statistically-provided functional relationships obtained from real world test data, or a combination of the two. This approach has certain limitations in capturing the effect of new technologies on CO 2 emission related policy initiatives. The present study proposes a new method for the detailed calculation of the European light duty vehicle fleet CO 2 emissions, which could help to overcome such limitations, achieve better results when making CO 2 emissions projections and better support future policies. Simulation at individual vehicle level is combined with fleet composition data, retrieved from the official European CO 2 emissions monitoring database, and publicly available data regarding individual vehicle characteristics in order to calculate vehicle CO 2 emissions and fuel consumption over different conditions and vehicle configurations. The methodology is applied to analyze and assess the impact of the introduction of the new certification procedure, the Worldwide Light duty vehicle Test Procedure (WLTP), on the European car fleet CO 2 emissions. Results show an average WLTP to NEDC CO 2 emissions ratio of approximately 1.2. The increases in CO 2 emissions are higher for cars exhibiting lower NEDC emission values (additional 29 and 25 gCO 2 /km for vehicles emitting 100 and 119 gCO 2 /km, respectively). At higher emission levels (about 250 CO 2 g/km) WLTP and NEDC present comparable results. Three possible scenarios for the translation of projected NEDC CO 2 emissions to WLTP-based ones are quantified. [ABSTRACT FROM AUTHOR]

Official laboratory-measured monitoring data indicate a progressive decline in the average fuel consumption and CO 2 emissions of the European passenger car fleet. There is increasing evidence to suggest that officially reported CO 2 values do not reflect the actual performance of the vehicles on the road. A reported difference of 30–40% between official values and real-world estimates was found which has been continuously increasing. This paper reviews the influence of different factors that affect fuel consumption and CO 2 emissions on the road and in the laboratory. Factors such as driving behaviour, vehicle configuration and traffic conditions are reconfirmed as highly influential. Neglected factors (e.g. side winds, rain, road grade), which may have significant contributions in fuel consumption in real world driving are identified. The margins of the present certification procedure contribute between 10 and 20% in the gap between the reported values and reality. The latter was estimated to be of the order of 40%, or 47.5 gCO 2 /km for 2015 average fleet emissions, but could range up to 60% or down to 19% depending on prevailing traffic conditions. The introduction of a new test protocol is expected to bridge about half of the present divergence between laboratory and real world. Finally, substantial literature was found on the topic; however, the lack of common test procedures, analysis tools, and coordinated activity across different countries point out the need for additional research in order to support targeted actions for real world CO 2 reduction. Quality checks of the CO 2 certification procedure, and the reported values, combined with in-use consumption monitoring could be used to assess the gap on a continuous basis. [ABSTRACT FROM AUTHOR]

A newly designed Compressed Natural Gas prototype engine was benchmarked against its parent Euro V compliant engine in terms of gaseous emissions and with particular view on regulated and Green House Gas emissions. The main technological innovation included a new cylinder head equipped with a Variable Valve Actuator system designed to increase the efficiency compared to the reference throttled engine. The objective of the study was to examine the effect of this system on the operation of the prototype engine. Engine stand-alone tests represented the first step of this analysis. Afterwards, both engines were installed on the same truck and tested under different operating conditions. Vehicle tests included measurements on a chassis dynamometer as well as on-road with the aim of verifying real-world emissions. CO 2 emissions and Brake Specific Fuel Consumption of the prototype were lower compared to the reference engine, with this phenomenon being more pronounced on-road. Furthermore, reduced NO x and CO emissions were observed under all operating conditions. On the other hand, the introduction of the prototype engine had a negative effect on CH 4 emissions. Despite that the prototype was initially designed to fulfill the EURO V standards, no pollutant exceeded the EURO VI limits over homologation cycles. [ABSTRACT FROM AUTHOR]

The European Commission is preparing a new regulatory initiative for monitoring CO 2 emissions and fuel consumption of Heavy-Duty Vehicles in Europe. The new methodology is based on a combination of component testing and computer simulation of the vehicles' fuel consumption. A study was launched aiming to demonstrate that the approach is accurate and representative of the actual performance of vehicles. Experiments were conducted on two trucks, a 40 t Euro VI long haul truck and an 18 t Euro V rigid truck. Measurements were performed both on the chassis dyno and on the road. Simulation software was used for simulating the tests. Its ability to capture vehicle performance and fuel consumption was assessed against the measured data. Simulation results closely matched those of the dyno tests with the final simulated fuel consumption deviating by about ±2–4% compared to the measured value. Over the tests performed on the road, the final fuel consumption laid within a ±3.5% from the measurement. Given the variability of the actual measurement (σ ≥ 2%), it is concluded that a future official vehicle certification scheme can be based on this approach and achieve both high representativeness, compared to the vehicle's actual performance and high vehicle-to-vehicle, accuracy. [ABSTRACT FROM AUTHOR]

In 2012 some 2.8 million toe of bioethanol were introduced in the European gasoline market. The introduction of ethanol blendstocks in the European fuels market should take place without undermining pollutant emissions or vehicle engine performance. According to the Euro 5 certification procedure the properties of three different ethanol blends supplied in the European market (E5, E75, E85) should be taken into account when testing for exhaust emissions. In this study the latest procedure established for emissions certification is assessed, shedding light on the gaseous regulated emissions and CO 2 – energy/fuel consumption performance of two Flex Fuel Vehicles with different fueling strategies (Direct/Port Fuel Injection) and different Euro standards (Euro 4 and Euro 5). Both legislative and non-legislative “real-world” driving cycles were used in the study. The analysis is completed with a comparison with existing emission factors for Flex Fuel Vehicles in Europe. At 22 °C CO emissions decreased over all conditions tested with the use of the high ethanol content fuel (E85), compared to the E5 performance. Total HC emissions were practically unaffected by the fuel type. NO x emissions decreased for both vehicles over the New European Driving Cycle, while over the Common Artemis Driving Cycle the vehicles exhibited different NO x behavior. At −7 °C both regulated CO and total HC emissions increased with E75 fuel. However, the Euro 5 vehicle exhibited emission performance below the current legislative limits for both CO/total HC over the cold-start urban part of the cycle. Results were found to be in line with existing emission factors used in Europe for ethanol-fueled vehicles. [ABSTRACT FROM AUTHOR]

Highlights: [•] Highest biodiesel blends result in increased SOF’s percentage to the DPM. [•] O-D SOF and inorganic ions seen not to be affected by the fuel change. [•] F-D SOF was the major constituent comprising 70–90% of total SOF. [•] DPF equipped vehicles exhibited lower oxidation activity per km compared to V2. [Copyright &y& Elsevier]

Highlights: [•] Tested Euro 4+ vehicles with 3 different exhaust aftertreatment systems. [•] Different diesel–biodiesel blends used over 4 different driving modes. [•] Limited increases observed in CO2 with the biofuel blends. [•] Both NO and NO2 increased with the concentration of biofuel in the blend. [•] Biodiesel decreased solid particles number and size in nonDPF equipped vehicle. [ABSTRACT FROM AUTHOR]

Abstract: The emissions of CO2 and regulated pollutants (NOx, HC, CO, PM) of thirteen Euro 5 compliant passenger cars (seven gasoline, six Diesel) were measured on a chassis dynamometer. The vehicles were driven repeatedly over the European type-approval driving cycle (NEDC) and the more dynamic WMTC and CADC driving cycles. Distance-specific emission factors were derived for each pollutant and sub-cycle, and these were subsequently compared to the corresponding emission factors provided by the reference European models used for vehicle emission inventory compilation (COPERT and HBEFA) and put in context with the applicable European emission limits. The measured emissions stayed below the legal emission limits when the type-approval cycle (NEDC) was used. Over the more dynamic cycles (considered more representative of real-world driving) the emissions were consistently higher but in most cases remained below the type-approval limit. The high NOx emissions of Diesel vehicles under real-world driving conditions remain the main cause for environmental concern regarding the emission profile of Euro 5 passenger cars. Measured emissions of NOx exceeded the type-approval limits (up to 5 times in extreme cases) and presented significantly increased average values (0.35g/km for urban driving and 0.56g/km for motorway driving). The comparison with the reference models showed good correlation in all cases, a positive finding considering the importance of these tools in emission monitoring and policy-making processes. [Copyright &y& Elsevier]

Abstract: This paper discusses the development and validation of passenger car emission factors, using real world operation data. In total, six passenger cars of different technologies were studied. The tested vehicles were operated under various driving conditions and over two different routes in the region of Lombardia, Italy. These routes were specifically defined in order to provide a range of driving conditions, including urban, rural and highway driving. Tailpipe emissions and exhaust gas flows were measured on-board the vehicle, using a portable emissions measurement system (PEMS). In addition, all vehicles were tested over the European type-approval driving cycle (NEDC) with the same PEMS equipment. The testing of gasoline vehicles showed that emissions are well below the emission standards and do not raise any concern. However, the testing of diesel vehicles both under real-world driving conditions and over the NEDC brought to the surface important concerns regarding the actual NO x emissions of modern diesel vehicles, since they seem to comply with the corresponding emission standard over the type-approval cycle, but they constantly exceed the specified limit when tested under real-world driving conditions. Results from real-world operation revealed that there is a significant deviation from the NO x emission standard limit (especially for the newly introduced Euro 5 technology). These observations raise concerns regarding the actual NO x emissions of modern vehicles and their impact on urban air-quality. The emission factors originally measured on the road are also compared to the corresponding COPERT average speed emission factors. In general, emissions of CO2, THC and CO correlate fairly well with COPERT, for all vehicles. In the case of NO x emissions, emission levels of the two tested Euro 5 diesel passenger cars are consistently higher in urban, rural, and highway driving compared to the corresponding COPERT emission factor. Thus, leading to the conclusion that more experimental data are necessary, especially for post-Euro 4 compliant diesel vehicles of different engine capacities particularly when it comes to NO x emissions from diesel vehicles. [Copyright &y& Elsevier]

Abstract: This paper attempts an integrated environmental assessment of certain crops, their products and by-products, which are promoted in Greece, as potential raw materials for liquid biofuel and low carbon energy production. The analysis is based on the experimental results of a Greek state funded research project (Hi-Bred fuels), which investigated the integrated management of energy crops for both biofuel and energy production. Four crops, some new for Greek agriculture and other indigenous, namely rapeseed, soya, sunflower and cotton, were cultivated under “real farming” conditions, keeping detailed data of all important aspects affecting their environmental profile. The main industrial processes employed in Greece for extracting, processing and esterifying vegetable oil from the oleiferous seeds were also identified and studied in detail. The data collected during the various production steps were introduced in Global Emission Model for Integrated Systems (GEMIS) software in order to create production cycle models of both non-esterified (straight vegetable oil) and esterified (biodiesel) biofuel models. Dedicated experiments were performed on a diesel passenger car in order to investigate the applicability of the final products. Results indicate that sunflower has the optimal environmental characteristics with respect to biofuel production with potential GHG savings of 58–71% depending on the end product. Rapeseed followed with GHG savings potential of 48%–62%, soyabean oil (47%–60%) and cottonseed oil (35%–47%). For the different products, and production steps, the results of the analysis for energy, CO2 equivalent emissions and other pollutant emissions are presented. Results concerning energy crops adaptability in Greek climate conditions and their product yields were quite promising, with the exception of the watering demands, which in some cases were not sustainable (GHG savings below 35%). Vehicle application results indicate that on a low level concentration (up to 10%v/v) all biofuels may be employed without important effects on vehicle emissions. Finally it is concluded that the use of residual waste biomass is a key aspect for achieving sustainable and environmentally efficient biofuels. [Copyright &y& Elsevier]

Abstract: This paper summarizes the results of an extensive experimental study aiming to evaluate the performance and pollutant emissions of diesel and CNG waste collection trucks under realistic and controlled operating conditions in order to support a fleet renewal initiative in the city of Milan. Four vehicles (1 diesel and 3 CNG) were tested in two phases using a portable emission measurement system. The first phase included real world operation in the city of Milan while the second involved controlled conditions in a closed track. Emissions recorded from the diesel truck were on average 2.4kg/km for CO2, 0.21g/km for HC, 7.4g/km for CO, 32.3g/km for NOx and 46.4mg/km for PM. For the CNG the values were 3.6kg/km for CO2, 2.19g/km for HC, 15.8g/km for CO, 4.38g/km for NOx and 11.4mg/km for PM. CNG vehicles presented an important advantage with regards to NOx and PM emissions but lack the efficiency of their diesel counterparts when it comes to CO, HC and particularly greenhouse gas emissions. This tradeoff needs to be carefully analyzed prior to deciding if a fleet should be shifted towards either technology. In addition it was shown that existing emission factors, used in Europe for environmental assessment studies, reflect well the operation for CNG but were not so accurate when it came to the diesel engine truck particularly for CO2 and NOx. With regard to NOx, it was also shown that the limits imposed by current emission standards are not necessarily reflected in real world operation, under which the diesel vehicle presented almost 4 times higher emissions. Regarding CO2, appropriate use of PEMS data and vehicle information allows for accurate emission monitoring through computer simulation. [Copyright &y& Elsevier]

Abstract: Straight vegetable oil (SVO) has been considered as a possible alternative to fossil diesel-engine fuel since the development of diesel engines. In Europe, SVOs achieved a measurable share in biofuels market reaching 4%. This study attempts to identify the impact of untreated SVO application on fuel consumption and emissions, regulated and non-regulated, on a Euro 3 common rail diesel passenger car. Three different vegetable oils (cottonseed, sunflower, and rapeseed) were blended with diesel fuel, on a 10–90% v/v ratio each. Chassis dynamometer measurements were conducted including both regulated and non-regulated pollutants. In the case of rapeseed oil–diesel blend, carbonyl compounds (10 aldehydes and ketones) were investigated. In addition to the legislated procedure (NEDC), the Artemis driving cycles were used for quantifying the fuels’ impact over realistic driving conditions. Results indicate that all blends have limited effects on gaseous pollutants and vehicle performance. Statistically significant increases on CO2, CO and HC were recorded over NEDC in the order of 3, 39 and 31%. Reductions were observed on PM emissions particularly for the sunflower oil blends, while NOx remained at baseline levels. Comparison with the emission levels measured when using esterified fuels of the same feedstocks suggests that SVO presence does not affect engine exhaust in the same way as biodiesel. The vegetable oil presence in the fuel appeared to suppress the formation of nucleation mode particles. Straight rapeseed oil increased carbonyl compound emissions over all cycles tested and resulted in higher acroleine/acetone presence in the carbonyl compound composition. [Copyright &y& Elsevier]

Abstract: Biodiesel (fatty acid methylesters) blends with fossil diesel at a mixing ratio between 0.5 and 5vol.% are widely offered as automotive fuels in Europe. The target for the future is to bring this ratio to at least 10%, in order to increase the share of renewable energy in transport. There is however limited evidence on the effects of such blends on the combustion and emissions of diesel engines not originally designed to operate on biodiesel blends. In this study, a number of experiments with 10 vol.% (B10) biodiesel fuel of palmoil origin were performed on a light-duty common-rail Euro 3 engine. The measurements included in-cylinder pressure, pollutants emissions, and fuel consumption. Combustion effects were limited but changes in the start of ignition and heat-release rate could be identified. Emission effects included both higher and lower smoke and NOx, depending on the operation point. The results on the engine bench were compared against a Euro 3 common-rail light-duty vehicle driven on the chassis dynamometer, in order to include the effects of emission control systems (EGR and oxidation catalyst). In addition to the palm biodiesel, an RME-diesel blend was also tested to examine the effects of a fuel with different characteristics. Both biodiesel blends reduced PM emissions and only marginal effects on NOx over the certification test could be identified. The results of this study show that up to 10% biodiesels could be used on current diesel vehicles, without significantly affecting vehicle emission performance. [ABSTRACT FROM AUTHOR]

Abstract: Biodiesel use as an automotive fuel is expanding around the world and this calls for better characterisation of its impact on diesel combustion, and emissions. A neat soybean-oil derived biodiesel (B100) and its 50vol.% blend with petroleum diesel (B50) were used on a Euro 2 diesel passenger car. Measurements of CO2, CO, HC, NO x , PM, particle number and size distribution and carbonyl compounds (aldehydes and ketones) were conducted on a chassis dynamometer. Acceleration tests were performed, fuel consumption was calculated and measured and metals concentration in the lubricant was determined, in order to assess the biodiesel impact on engine performance and wear. Tests were conducted over the certification cycle and real-world driving cycles. Results showed that biodiesel presence had a negative impact under cold start conditions on both regulated emissions and fuel consumption. However the picture was different in the case of warm start real-world cycles, where differentiations were limited and in several cases biodiesel had a beneficial effect on emissions and efficiency. Regarding particle number, solid particles decreased with biodiesel but total particles increased. Certain carbonyl compounds were also increased with B100. Overall, biodiesel at high blending ratios may strongly impact emissions, in a rather non-uniform manner, with the actual effect being dependant on driving conditions and blending ratio. Some of the differentiations observed were not expected when compared to similar results presented in the literature. However this study does not reach definitive conclusions but rather presents a case that may appear in the European passenger car fleet, which requires further attention and research. [Copyright &y& Elsevier]

The reduction of transport-generated CO2 emissions is currently a problem of global interest. Hybrid electric vehicles (HEVs) are considered as one promising technological solution for limiting transport-generated greenhouse gas emissions. Currently, the number of HEVs in the market remains limited, but this picture will change in the years to come as HEVs are expected to pave the way for cleaner technologies in transport. In this paper, results are presented regarding fuel economy and pollutant emissions measurements of two hybrid electric production vehicles. The measurements were conducted on a Prius II and a Honda Civic IMA using both the European legislated driving cycle (New European Driving Cycle, NEDC) and real-world simulation driving cycles (Artemis). In addition to the emissions measurements, other vehicle-operating parameters were studied in an effort to better quantify the maximum CO2 reduction potential. Data from real-world operation of a Prius II vehicle were also used in the evaluation. Results indicate that in most cases both vehicles present improved energy efficiency and pollutant emissions compared to conventional cars. The fuel economy benefit of the two HEVs peaked under urban driving conditions where reductions of 60% and 40% were observed, respectively. Over higher speeds the difference in fuel economy was lower, reaching that of conventional diesel at 95kmh−1. The effect of ambient temperature on fuel consumption was also quantified. It is concluded that urban operation benefits the most of hybrid technology, leading to important fuel savings and urban air quality improvement. [Copyright &y& Elsevier]

The reduction of CO2 emissions and fuel consumption from road transportation constitutes an important pillar of the EU commitment for implementing the Kyoto Protocol. Efforts to monitor and limit CO2 emissions from vehicles can effectively be supported by the use of vehicle modelling tools. This paper presents the application of such a tool for predicting CO2 emissions of vehicles under different operating conditions and shows how the results from simulations can be used for supporting policy analysis and design aiming at further reductions of the CO2 emissions. For this purpose, the case of light duty goods (N1 category) vehicle CO2 emissions control measures adopted by the EU is analysed. In order to understand how certain design and operating aspects affect fuel consumption, a number of N1 vehicles were simulated with ADVISOR for various operating conditions and the numerical results were validated against chassis dynamometer tests. The model was then employed for analysing and evaluating the new EU legislative framework that addresses CO2 emissions from this vehicle class. The results of this analysis have shown the weaknesses of the current regulations and revealed new potential in CO2 emissions control. Finally the TREMOVE model was used for simulating a possible scenario for reducing CO2 emissions at fleet level. [Copyright &y& Elsevier]

[Display omitted] • Three sampling approaches were investigated for estimating HDV fleet CO2 emissions. • Mean CO 2 emissions deviate less than 2% in the best cases and less than 5% overall. • The JDE sampling preserves well the distribution characteristics. • MEDP and MSD are suitable to investigate fleet emissions when limited data are available. • The alternative methodologies can be used to predict CO 2 emissions in future fleet scenarios. Certification and monitoring of heavy vehicle CO 2 emissions in several countries are based on individual vehicle simulation. Smaller fleet subsets can be used for accurate fleet-level results while preserving the characteristics of the underlying fleet-emissions distributions. The paper focuses on three approaches to capture fleet CO 2 emissions: a) sampling directly from the fleet-data, b) sampling from data of individual vehicle components and c) using key statistics regarding the fleet composition that are available. The first and second approach deliver marginal divergences of the mean, between 1.1 and 2.1% and below 2.7 respectively, preserving the characteristics of the distribution. The third deviated by up to 5%, but lacked the detailed characteristics of the underlying statistical distribution. All three are useful when setting up fleet-wide monitoring schemes where detailed data are not available and to investigate the potential CO 2 savings of various future fleet compositions, and scenarios regarding the diffusion of different types of technologies. [ABSTRACT FROM AUTHOR]

Emissions from vehicles can be measured on the road or in laboratories using dynamometers that simulate the forces that a vehicle is subject to while driving on the road. In the light-duty vehicle regulations, only roller-type dynamometers are allowed. For hub-type dynamometers, due to the direct connection of the dynamometers to the wheel hubs, additional parameters that are used are rotational mass, dynamic wheel radius, and the tire force–slip relationship. Following up on an experimental study which showed that equivalent emission results can be achieved between roller- and hub-type dynamometers, this work presents and evaluates methods to determine parameters used by a hub-type dynamometer for mimicking roller-type dynamometer behavior. It also discusses methods to determine the parameters to simulate specific road conditions or when using only a hub-type dynamometer. The results show that using a constant dynamic radius for each wheel and a linear tire force–slip relationship is sufficient for emission measurement because typical errors in these parameters are practically negligible. A typical error in rotational mass results in a minor error in the determined forces during coast down, but the typical accuracy of this parameter is in parity with the difference allowed in the regulation. The final conclusion is that using the information already stated in the certificate of conformity (CoC) of the vehicle (for the coast down), and reasonably set parameters for wheel dynamic radius and the tire slip–force relationship, hub-type dynamometers should yield equivalent results to roller-type dynamometers. [ABSTRACT FROM AUTHOR]

This study investigates the CO2 reduction potential of powertrain hybridisation on heavy-duty lorries and city buses. The analysis considers modern parallel and serial hybrid architectures, assessing their efficiency and limits in CO2 emission reduction through vehicle simulation in VECTO, which is the official tool of the European Commission for calculating heavy-duty vehicle fuel and energy consumption. The results reveal distinct trends for each vehicle type and architecture. In lorries, more significant improvements are observed in urban delivery profiles, reaching up to ~16%, indicating the benefits of hybridisation in transient conditions with energy recuperation opportunities. City buses, particularly those with serial architectures, exhibit significant emission reductions that reach 36%, making them suitable for urban environments. The optimisation of electric motor size and performance plays a crucial role in achieving emission reductions, while battery capacity must be carefully considered to avoid adverse effects. For lorries in urban delivery use, further improvements of 17.5% can be achieved by utilising a 160 kW engine motor and 30 kWh battery. Buses are already quite well optimised, with serial architecture presenting the highest benefits with a 120 kW electric motor and a battery of 11 kWh. Future research should focus on supercapacitors and gearboxes to improve efficiency at higher vehicle speeds and assess hybridisation potential in interurban coach travel. The heavy-duty vehicle sector can make significant strides towards low-carbon transport by maximising hybrid powertrain efficiency and emission reductions. [ABSTRACT FROM AUTHOR]

Drivers' heterogeneity and the broad range of vehicle characteristics on public roads are primarily responsible for the stochasticity observed in road traffic dynamics. Understanding the behavioural differences in drivers (human or automated systems) and reproducing observed behaviours in microsimulation has lately attracted significant attention. Calibration of car-following model parameters is the prevalent way to chracterize different driving behaviours. However, most car-following models do not realistically reproduce free-flow accelerations and therefore, model parameters are usually mainly the result of over-fitting with limited possibility to reproduce realistic drivers' heterogeneity in simulation. To solve this problem, the present study proposes a novel framework to identify individual driver fingerprints based on their acceleration behaviours and reproduce them in microsimulation. The paper also discusses the unsuitability of vehicle acceleration to properly characterise alone the aggressiveness of a driver. A large experimental campaign and simulation results demonstrate the robustness of the proposed method. [ABSTRACT FROM AUTHOR]

Background: Surging acceptance of adaptive cruise control (ACC) across the globe is further escalating concerns over its energy impact. Two questions have directed much of this project: how to distinguish ACC driving behaviour from that of the human driver and how to identify the ACC energy impact. As opposed to simulations or test-track experiments as described in previous studies, this work is unique because it was performed in real-world car-following scenarios with a variety of vehicle specifications, propulsion systems, drivers, and road and traffic conditions. Methods: Tractive energy consumption serves as the energy impact indicator, ruling out the effect of the propulsion system. To further isolate the driving behaviour as the only possible contributor to tractive energy differences, two techniques are offered to normalize heterogeneous vehicle specifications and road and traffic conditions. Finally, ACC driving behaviour is compared with that of the human driver from transient and statistical perspectives. Its impact on tractive energy consumption is then evaluated from individual and platoon perspectives. Results: Our data suggest that unlike human drivers, ACC followers lead to string instability. Their inability to absorb the speed overshoots may partly be explained by their high responsiveness from a control theory perspective. Statistical results might imply the followers in the automated or mixed traffic flow generally perform worse in reproducing the driving style of the preceding vehicle. On the individual level, ACC followers have tractive energy consumption 2.7–20.5% higher than those of human counterparts. On the platoon level, the tractive energy values of ACC followers tend to consecutively increase (11.2–17.3%). Conclusions: In general, therefore, ACC impacts negatively on tractive energy efficiency. This research provides a feasible path for evaluating the energy impact of ACC in real-world applications. Moreover, the findings have significant implications for ACC safety design when handling the stability-responsiveness trade-off. [ABSTRACT FROM AUTHOR]

Highlights • Relation between consumption and average speed for ICEV is questioned for PEV. • For PEVs higher energy consumption is connected to the free-flow test-cases. • Need to rethink the connection between congestion and energy inefficiency. • Results are based on real and simulated vehicle trajectories. Abstract Decreasing road transport's harmful effects on environment and health and reducing road accidents are major policy priorities. A variety of technologies could drastically improve air quality, reduce energy consumption and CO 2 emissions of road vehicles: in this respect, a prominent trend leverages Electric Vehicles (EVs), supported by improved performance and energy efficiency through connectivity and automation. A noteworthy research question in the transition from Internal Combustion Engine Vehicles (ICEVs) to the alternative technologies, is to understand how Intelligent Transport Systems and other traffic-related measures can contribute to the reduction of fuel consumption and greenhouse gas emissions. In fact, a widely acknowledged tenet assumes that congestion removal or mitigation in presence of ICEVs implies also a reduction of transport-related externalities. This paper explores whether this effect still holds for EVs, by performing an analysis of energy consumption over different vehicle trajectories, under both congested and free-flow conditions. Calculations are carried out using two vehicle simulators: the VT-CPEM (Virginia Tech Comprehensive Power-based Energy consumption model) model for EVs and the CO 2 MPAS (CO 2 model for Passenger and commercial vehicle Simulation) vehicle simulator for the ICEVs, for both electric and conventional cases passengers and freight/commercial powertrains have been analysed. Results are presented on real and simulated data related to four powertrain-vehicle combinations, in terms of general trends of energy/fuel consumption versus speed. Interestingly, results show that, differently from ICEVs, the relationship between congestion and energy consumption underlying EVs can change with higher energy consumption connected to an increased average traffic speed. [ABSTRACT FROM AUTHOR]

Plug-in Hybrid Electric Vehicles (PHEV) can be classified as low CO 2 emissions vehicles in Europe if they emit no more than 50 g/km, and are viewed as favourable transitional technology for road transport electrification. Some recent studies challenge their effectiveness in reducing CO 2 emissions in real-world conditions. This study tested four Euro 6 PHEVs, both in the laboratory and on the road, for CO 2 emissions and energy consumption. The experimental results show that PHEVs in-use CO 2 emissions can range from 0 to 6 times the official type-approval CO 2 value. The results were analysed to derive relevant operation models and emission factors and benchmark their in-use performance with respect to the officially declared consumption values. A three-dimensional CO 2 emissions model is proposed based on charge level and average trip speed or wheel energy. When considering different users' charging practices and representative real-world conditions, PHEVs in-use CO 2 emissions are 1.5–2 times the official type-approval CO 2 value. Although the real-world emissions of plug-in hybrids appear to increase compared to the official values, they generally remain lower than conventional powertrains. The single-modelling element approach presented offers a novel, robust, and simple to implement way to include PHEVs in planning exercises, emissions calculation models to support national and regional inventories, lifecycle emissions estimates, and fleet-wide emissions monitoring tools. [ABSTRACT FROM AUTHOR]

Particulate mass concentration is a crucial parameter for characterising air quality. The diesel particulate filter (DPF) is the primary technology used to limit vehicle particle emissions, but it needs periodic cleaning, a process called regeneration. This study aims to assess the impact of active DPF regeneration on the performance and emissions of Euro 5 and 6 vehicles. The study examined both carbon dioxide (CO2) and pollutant (nitrogen oxides (NOx) and particle number (PN)) emissions for eight vehicles tested in the laboratory and on the road. Apart from the DPF, a wide range of emission control systems was covered in this experimental campaign, including exhaust gas recirculation (EGR), diesel oxidation catalyst (DOC), lean NOx trap (LNT) and selective catalytic reduction (SCR) catalyst, revealing the different impacts on NOx emissions. The regeneration frequency and duration were also determined and used to calculate the Ki factor, which accounts for the emissions with and without regeneration, weighted over the distance driven between two consecutive regeneration events. Based on these outcomes, representative emission factors (EF) were proposed for the regeneration phase only and the complete regeneration interval. In addition, the effect of regeneration on efficiency was estimated and compared with other energy consumers. The results indicated a significant impact of DPF regeneration on CO2, NOx and PN emissions, higher in the case of driving cycle testing in the laboratory. The relevant mechanisms behind the elevated emission levels were analysed, focusing on the regeneration period and the test phase following immediately after. The calculation of the Ki factor and the comparison with the official values revealed some weaknesses in its application in real-world conditions; to overcome these, new NOx EF values were calculated, depending on the emission control system. It was revealed that Euro 6 vehicles equipped with SCR could comply with the applicable limits when considering the complete regeneration interval. Finally, it was indicated that the DPF regeneration impact on vehicle efficiency is similar to that of driving with the air conditioning (A/C) system and headlights on. [ABSTRACT FROM AUTHOR]

The present study explores net carbon-neutral road transport options in the EU27 in 2050 from a well-to-wheel (WtW) perspective. To this aim, three scenarios have been developed regarding the evolution of the road vehicle fleet composition in terms of the degree of electrification of powertrains, and technical measures such as vehicle efficiency improvements, transport flow, and transport volumes have been considered. The fleet scenarios are further combined with four scenarios deploying different mixes of alternative fuels in 2050, including electricity, e-fuels, liquid/gaseous advanced biofuels and remaining fossil fuel components. Two different electricity production pathways are considered, as well, one of them assuming fully renewable electricity production, and an alternative one including residual shares of nuclear and natural gas power plants plus carbon capture and storage. The Joint Research Centre's DIONE model was used for the scenario calculations. From a tank-to-wheel (TtW) perspective, each scenario reduces energy consumption, mainly due to powertrain electrification, with EU27 TtW road vehicle energy consumption in 2050 ranging from roughly 650 to 1650 TWh, which is 20%–53% of that of 2019. For the most strongly electrified fleet scenario with optimistic assumptions on measures to improve vehicle efficiency, transport flow and transport volumes and renewable electricity production, well-to-tank (WtT) energy consumption is around 110–160 TWh, depending on the fuel scenario. If a moderately electrified fleet is propelled with e-fuels, even when assuming fully renewable electricity and optimistic measures, the WtT energy consumption increases ten times or more, to 1300 TWh (2150 TWh with pessimistic measures). The results show that fleet electrification is the strongest lever for WtW transport energy consumption reduction among the options considered. Other efficiency measures contribute significantly to energy savings, but their benefit decreases with increasing fleet electrification. The production pathways of fuels make a substantial difference for WtW fleet energy requirement if the fleet is moderately electrified, in which case e-fuels require significant amounts of additional renewable electricity. Nevertheless, fuel production pathways become irrelevant from an energetic point of view under very ambitious electrification scenarios since fuel volumes become marginal. The economic feasibility and the societal acceptability of different pathways towards WtW carbon-neutrality of road transport is out of scope of this paper and requires further investigation. • The study examines well-to-wheel scenarios for 2050 carbon neutral road transport. • Electrification is the strongest driver in transport energy consumption reduction. • Vehicle efficiency and activity impacts decrease with fleet electrification. • With high fleet electrification fuel production barely impacts energy consumption. • E-fuels require particularly large amounts of additional renewable electricity. [ABSTRACT FROM AUTHOR]

Abstract: The effect of biodiesel on emissions of diesel passenger cars is a combination of the fuel properties, the blending ratio, and the vehicle technology. In this study, saturated and unsaturated biodiesel fuels were tested neat (B100) and in 30% blend with fossil diesel (B30) on two Euro 3 diesel passenger cars of different engine technologies, namely common rail and unit injector. The measured dataset is enlarged by introducing B10 results from an earlier study in order to produce generalized conclusions over a wider range of blends. None of these vehicles was equipped with a particle filter and different conclusions might be reached for filter-equipped vehicles. The results indicate that the influence of biodiesel on pollutant emissions primarily depends on the blending ratio and secondly on the level of unsaturation and engine technology. Tailpipe CO2, NO x and PM emissions with biodiesel varied from −1% to +3%, −1% to 14%, and −18% to −35%, respectively, compared to fossil diesel. The difference over fossil diesel generally increased with an increasing blending ratio. CO and HC emissions increased over the fossil diesel but remained at low levels and did not threaten the compliance of the vehicles with their respective emission limits. Use of biodiesel on the common rail vehicle led to a smaller NO x increase and a higher PM reduction than in the unit-injector case. The unsaturated fuel generally led to higher NO x emissions from both engine technologies. However, the maximum blending ratio of saturated biodiesel is limited to around B30 due to cold-flow limitations. Hence, the saturated vs. unsaturated species ratio should be carefully designed in market fuels in order to optimize environmental and operational benefits. Overall, it appears that blends up to 10% v/v may be introduced with limited urban air quality implications. [Copyright &y& Elsevier]

Abstract: This study investigates the impact of mid-high biodiesel blends on the criteria and PAH emissions from a pick-up diesel vehicle. The vehicle was a Euro 4 (category N1, subclass III) compliant common rail light duty vehicle fitted with a diesel oxidation catalyst. Emission and fuel consumption measurements were performed on a chassis dynamometer using constant volume sampling (CVS) technique, following the European regulations. All measurements were conducted over the NEDC and Artemis driving cycles. Aiming to evaluate the fuel impact on emissions, a soy-based biodiesel, a palm-based biodiesel, and an oxidized biodiesel obtained from used frying oils were blended with an ultra low sulfur diesel at proportions of 30%, 50% and 80% by volume. CO2 emissions and fuel consumption exhibited increases with biodiesel over all driving conditions which ranged up to 5%. NO x emissions were found to be above the Euro 4 limit and increased with biodiesel between 5% and 10% except for the blends prepared with the palm-based methyl ester. The emissions of PM, HC, and CO decreased with the addition of biodiesel reaching maximum reductions in the order of 10%, 30% and 20% respectively; however, some increases were observed over the NEDC which may be attributed to cold-start. Sharp increases in most PAH, nitro-PAH and oxy-PAH compounds were observed with the application of biodiesel. These increases were particularly noticeable with the use of the oxidized blends, a phenomenon that it is related with the type and quality of this fuel. The emissions were also affected by the operating conditions of the engine. It was found that most PAH compounds were decreased as the mean speed and load of the driving cycle increased. [Copyright &y& Elsevier]

Abstract: This study investigates the impact of low concentration biodiesel blends on the regulated and particle-bound polycyclic aromatic hydrocarbon (PAH) emissions from a modern passenger car. Emissions measurements were performed on a chassis dynamometer using constant volume sampling technique, following the European regulations. All measurements were conducted over the New European Driving Cycle (NEDC) and the Artemis driving cycles. Aiming to evaluate the fuel impact on emissions, a soy-based, a palm-based, and a rapeseed oil based biodiesel were blended with diesel fuel at proportions of 10, 20, and 30% by volume. The emissions of PM, HC, and CO decreased with biodiesel over most driving conditions. Some increases were observed over the NEDC, which may be attributed to the cold-start effect and to certain fuel characteristics. NOx emissions increased with biodiesel and strongly were dependent to the degree of unsaturation of the fuel. CO2 emissions and fuel consumption followed similar patterns and increased with biodiesel. PAH emissions presented discordant results, leading to the hypothesis that the influence of biodiesel source material was particularly strong on the formation of these pollutants. Both increases and decreases were observed in PAH, nitrated PAH and oxygenated PAH compounds with the use of biodiesel blends. [Copyright &y& Elsevier]

Abstract: This study explores the impact of neat soy-based methyl ester and its 50% v/v blend with low sulphur automotive diesel on PAH, nitro-PAH and oxy-PAH emissions of a Euro 2 compliant diesel passenger car tested on a chassis dynamometer. Emission measurements were evaluated for the certification NEDC, a hot-start UDC (urban part of NEDC) and the non-legislated Artemis driving cycles which simulate urban, rural and highway driving conditions in Europe. Overall, 16 PAHs, 4 nitro-PAHs and 6 oxy-PAHs were determined in the exhaust. The results obtained, showed that PAH emissions decreased with the addition of biodiesel during all driving modes. However, their nitrated and oxygenated products were found to increase with biodiesel compared to diesel fuel. The use of pure biodiesel led in some increases in PAH emissions when compared to its 50% blend. PAH emissions were also found to be adversely influenced by cold-start conditions and certain fuel properties. [Copyright &y& Elsevier]

The EU aims to substantially reduce its greenhouse gas emissions in the following decades and achieve climate neutrality by 2050. Better CO2 estimates, particularly in urban conditions, are necessary for assessing the effectiveness of various regional policy strategies. In this study, we measured the CO2 emissions of a Euro 6d-temp gasoline direct injection (GDI) vehicle with a three-way catalyst (TWC) and a gasoline particulate filter (GPF) at ambient temperatures from −30 °C up to 50 °C with the air-conditioning on. The tests took place both on the road and in the laboratory, over cycles simulating congested urban traffic, dynamic driving, and uphill driving towing a trailer at 85% of the maximum payloads of both the car and the trailer. The CO2 values varied over a wide range depending on the temperature and driving conditions. Vehicle simulation was used to quantify the effect of ambient temperature, vehicle weight and road grade on the CO2 emissions. The results showed that vehicle energy demand was significantly increased under the test conditions. In urban trips, compared to the baseline at 23 °C, the CO2 emissions were 9–20% higher at −10 °C, 30–44% higher at −30 °C, and 37–43% higher at 50 °C. Uphill driving with a trailer had 2–3 times higher CO2 emissions. In motorway trips at 50 °C, CO2 emissions increased by 13–19%. The results of this study can help in better quantification of CO2 and fuel consumption under extreme conditions. Additional analysis on the occurrence of such conditions in real-world operation is advisable. [ABSTRACT FROM AUTHOR]

• Novel method to estimate on-road resistance forces for road vehicles. • Method based on real-world experiments using wheel torque recordings. • Method's air drag error Standard Deviation of the Mean up to 2.98%. • Up to 5% variation in cycle energy demand from on-road coefficients versus official. • Policy relevance for acceptance limits for verification of vehicles in-service. Tyre rolling resistance and air drag significantly affect road-vehicle fuel and energy consumption. Their importance is recognised in vehicle certification regulations and standards worldwide. Detailed methodologies for their determination exist that require testing in dedicated proving grounds or specialised test facilities outside of actual driving conditions. As countries strive to improve vehicle efficiency, in-use verification of vehicle resistances will become essential for research and vehicle homologation. Multiple factors may limit such activities such as cost, lack of dedicated test infrastructure and equipment, and incompatibility with other vehicle-related tests that already take place. This study proposes a new method for determining vehicle resistances during on-road measurements based on wheel torque data. The method allows less expensive, more versatile test procedures that could be applied to a wide sample of vehicles across the fleet. The method was evaluated experimentally with nine vehicles (3 light-duty, 6 heavy-duty). Repeatability tests showed that the air drag error standard deviation ranged from 1 to 5.5 % for light-duties, and the pooled error standard deviation was 5.8 % among all heavy-duty vehicles. The results showed a divergence from the target cycle energy demand of <5 % during the on-road tests, a limit indicating the highest expected test discrepancy due to test uncertainties. Vehicle fuel consumption was simulated with both the measured and official resistance coefficients as a secondary validation. The on-road calculated coefficients led to accurate estimates of real-world consumption. The study discusses the impact of the wind vector during the test on the air drag and resistances' influence on consumption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel predictive ECMS algorithm for hybrid trucks based on projected power demand. • Algorithm operation validated on commercial plug-in hybrid electric truck. • Up to 5.9% energy efficiency gains over a municipal operation profile. • Power-predictive ECMS for energy management brings real CO 2 benefits. This paper examines potential fuel consumption savings through the implementation of a predictive equivalent consumption minimisation strategy, as a control algorithm in the energy management system of hybrid heavy-duty vehicles. A plug-in hybrid electric truck simulation model was developed as a demonstrator and was validated with experimental data. The baseline vehicle model was based on the same algorithm as VECTO, which is further extended in the current study by novel factors that contain the average predicted power demand. The potential benefits of the proposed algorithm are examined for different heavy-duty categories over regulatory mission profiles in both charge-sustain and charge-depletion modes. The results show that the fuel consumption can be reduced by up to 5.9 % and 4.4% in charge sustaining and charge depleting modes, respectively, depending on the mission profile. If such an algorithm is adopted by commercial vehicles, this could lead to substantial CO 2 and fuel consumption savings on the road. [ABSTRACT FROM AUTHOR]

The efforts to reduce CO 2 emissions from road transport have focused mainly on passenger cars, but the attention shifts to heavy-duty vehicles, which contribute significantly to the sector's greenhouse gas emissions despite their low fleet share. The current study focused on a bus and investigated the effect of environmental conditions and passenger occupancy on auxiliary usage and CO 2 emissions. It utilised measurements conducted over the Zincirlikuyu – Avcilar route in Istanbul, Turkey, to develop vehicle simulation models. The vehicle was simulated under different environmental conditions and passenger occupancy, and it was found that the auxiliary use could differ between −1.05 and 2.67 kW compared to the European reference conditions. Simulations with variable passenger capacity showed no difference with runs that utilised a standard average passenger capacity value. In addition, a factorial analysis was performed to cover a broader range of environmental conditions. The findings were used to develop a methodology to calculate vehicle-specific CO 2 emissions under different on-road conditions by utilising the vehicle's reference emissions. The study results are expected to contribute to the field as HVAC energy demands could increase on-road CO 2 emissions and limit the range of electrified powertrains. • Environmental conditions and occupancy significantly affect energy consumption and CO 2 emissions. • Power demands ranged from 0.7 kW to 6.8 kW, depending on environmental conditions and occupancy. • Actual HVAC energy demands could differ up to 2.8 kW from reference conditions. • The mean divergence of power demands over the year was about 4.8%. • No significant impact due to occupancy variability compared to using a standard occupancy. [ABSTRACT FROM AUTHOR]

Although Hybrid Electric Vehicles (HEVs) represent one of the key technologies to reduce CO2 emissions, their effective potential in real world driving conditions strongly depends on the performance of their Energy Management System (EMS) and on its capability to maximize the efficiency of the powertrain in real life as well as during Type Approval (TA) tests. Attempting to close the gap between TA and real world CO2 emissions, the European Commission has decided to introduce from September 2017 theWorldwide Harmonized Light duty Test Procedure (WLTP), replacing the previous procedure based on the New European Driving Cycle (NEDC). The aim of this work is the analysis of the impact of different driving cycles and operating conditions on CO2 emissions and on energy management strategies of a Euro-6 HEV through the limited number of information available from the chassis dyno tests. The vehicle was tested considering different initial battery State of Charge (SOC), ranging from 40% to 65%, and engine coolant temperatures, from -7 °C to 70 °C. The change of test conditions from NEDC to WLTP was shown to lead to a significant reduction of the electric drive and to about a 30% increase of CO2 emissions. However, since the specific energy demand of WLTP is about 50% higher than that of NEDC, these results demonstrate that the EMS strategies of the tested vehicle can achieve, in test conditions closer to real life, even higher efficiency levels than those that are currently evaluated on the NEDC, and prove the effectiveness of HEV technology to reduce CO2 emissions. [ABSTRACT FROM AUTHOR]

This paper analyses historical energy consumption trends of the EU road transport sector and examines the role of key determinants, such as economic and population growth, fuel prices, passenger and tonne-kilometres and vehicle fleet characteristics. In light of the EU 2030 and 2050 energy and climate targets, the paper assesses the energy efficiency and decarbonisation progress from 2000 to 2018. A detailed analysis is carried out using a balanced panel dataset from 1995 to 2018 and a test for causality between energy consumption and the selected explanatory variables. The results suggest that the declining trend of the normalised energy consumption of cars, trucks and light vehicles, which both dropped significantly in 2018 compared to 2000, can be related to energy efficiency and decarbonisation policies adopted by the EU and its Member States over the studied period. Decomposition analysis based on the Logarithmic Mean Divisia Index technique confirms the role of energy efficiency gains in curbing energy consumption of road transport, even with the strong upward force exerted by motorisation and population effects, especially in passenger transport. It also suggests that during the recession years (2008–2013), road transport consumption fell due to a sharp drop in the mileage but not in the motorisation effect, which continued to drive up consumption even in this period. Despite some positive developments, the increased demand for road transportation has led to continued energy consumption growth. This has been further compounded by differences between real-world and vehicle certification fuel consumption data. The article highlights the need to strengthen the current policy framework at the EU and MS levels in the next decade to reach the long-term decarbonisation targets. In the context of these targets, a more in-depth investigation of the real impact of energy efficiency and decarbonisation efforts will also become increasingly important. [ABSTRACT FROM AUTHOR]

The study proposes a methodology for quantifying the impact of real-world heterogeneous driving behavior on vehicle energy consumption, linking instantaneous acceleration heterogeneity and CO 2 emissions. Data recorded from 20 different drivers under real driving are benchmarked against the Worldwide Harmonized Light Vehicle Test Cycle (WLTC), first by correlating the speed cycle with individual driver behavior and then by quantifying the CO 2 emissions and consumption. The vehicle-Independent Driving Style metric (IDS) is used to quantify acceleration dynamicity, introducing driving style stochasticity by means of probability distribution functions. Results show that the WLTC cycle assumes a relatively smooth acceleration style compared to the observed ones. The method successfully associates acceleration dynamicity to CO 2 emissions. We observe a 5% difference in the CO 2 emissions between the most favourable and the least favourable case. The intra-driver variance reached 3%, while the inter-driver variance is below 2%. The approach can be used for quantifying the driving style induced emissions divergence. [ABSTRACT FROM AUTHOR]

The Worldwide Harmonized Light Duty Test Procedure (WLTP), recently issued as GTR15 by UNECE-WP29, is designed to check the pollutant emission compliance of Light Duty Vehicles (LDVs) around the world and to establish the reference vehicle fuel consumption and CO2 performance. In the course of the development of WLTP, the Joint Research Center (JRC) of the European Commission has tested gaseous emissions of twenty-one Euro 4-6 gasoline and diesel vehicles, on both the current European type approval test procedure (NEDC) and the progressive versions of the WLTP. The results, which should be regarded just as an initial and qualitative indication of the trends, demonstrated minimal average differences between CO2 emissions over the NEDC and WLTP. On the other hand, CO2 emissions measured at JRC on the NEDC were on average 9% higher than the respective type approval values, therefore suggesting that for the tested vehicles, CO2 emissions over WLTP were almost 10% higher than the respective NEDC type approval values. That difference is likely to increase with application of the full WLTP test procedure. Measured THC emissions from most vehicles stayed below the legal emission limits and in general were lower under the WLTP compared to NEDC. Moving from NEDC to WLTP did not have much impact on NOx from gasoline vehicles and CO from diesel vehicles. On the contrary, NOx from diesel vehicles and CO from low-powered gasoline vehicles were significantly higher over the more dynamic WLTP and in several cases exceeded the emission limits. Results from this study can be considered indicative of emission patterns of modern technology vehicles and useful to both policy makers and vehicle manufacturers in developing future emission policy/technology strategies. [ABSTRACT FROM AUTHOR]

Mandatory targets are set in Europe for Carbon Dioxide (CO 2) emissions of light-duty vehicles. EU law recognises the potential of certain innovative technologies to contribute to reducing CO 2 emissions. Vehicle systems and innovations are becoming increasingly complex, and the accurate quantification of their benefits increasingly difficult. The study investigates the potential of the CO 2 MPAS simulator to serve this purpose. Two innovative technologies were studied, Light-emitting diode (LED) lighting systems, efficient alternators (EA), and their combination. The model was validated on detailed test results from eight vehicles. A total of 452 passenger cars, for which test data were available, were subsequently simulated using CO 2 MPAS simulator. The mean simulated CO 2 savings was 0.91gCO 2 /km (LED lights), 0.98 gCO 2 /km (EA), and 1.78 gCO 2 /km (combined). Results show that simulated CO 2 savings were comparable to those calculated using the existing standardised method. For gasoline and diesel vehicles respectively, the difference in CO 2 savings between simulated and existing method was 2.8% and 0.14% in the LED lights case, and 0.6% and 0.67% in the alternator case. In the combined case, the difference was calculated to be 1.7% and 0.34%. Similar approaches could be used in the future for accurately capturing the benefits of more complex technologies. • Assessed the application of software simulation for eco-innovative technologies. • CO 2 savings from two technologies were simulated with high accuracy. • Simulation could support the evaluation of CO2 savings from such technologies. • Efficient lighting system or alternator save about 1 gCO 2 /km per vehicle. • Efficient lighting system and alternator combined save up to 1.8 gCO 2 /km per vehicle. [ABSTRACT FROM AUTHOR]

Integrated photovoltaics are an emerging technology which can extend the range of electric vehicles. However, up to now there is a lack of a consensus method that would provide consumers with an estimate of the fraction of annual driving which could be covered by solar power generated onboard in different usage scenarios and locations. To address this, we assess the energy implications of vehicle integrated photovoltaics for a commuter car and light delivery van for six climatic regions and for typical daily usage profiles over a ten-year period. The analysis captures the energy needs for driving and cabin temperature control to an unprecedented level of detail. Our results reveal that the grid power needed to drive such vehicles on identical routes can vary by more than 44% between climate regions. In the best case the solar power generated can cover up to 35% of the driving range per year. This contribution can vary by a factor of 2.5 between different climates, from 1800 to 5100 km annually, considerably mitigating the effect of ambient conditions on electric range. We propose developing consumer labels for solar electric vehicles that would consider this variation according to climatic conditions. The method described in this paper could help to frame initial discussions for such labels. We identify further requirements for research and development, standardisation, and policy needs. • Above 5000 km solar range possible for commuter car and van with integrated PV. • Ten year simulation reveals solar range differences by factor 2.5 across climates. • Over 44% difference in grid electricity needs across six climates globally. • At the moment vehicle integrated PV not financially viable. • Consumer labels for PVEV may be needed to inform about performance variations. [ABSTRACT FROM AUTHOR]

Integrated photovoltaics are an emerging technology which can extend the range of electric vehicles. However, up to now there is a lack of a consensus method that would provide consumers with an estimate of the fraction of annual driving which could be covered by solar power generated onboard in different usage scenarios and locations. To address this, we assess the energy implications of vehicle integrated photovoltaics for a commuter car and light delivery van for six climatic regions and for typical daily usage profiles over a ten-year period. The analysis captures the energy needs for driving and cabin temperature control to an unprecedented level of detail. Our results reveal that the grid power needed to drive such vehicles on identical routes can vary by more than 44% between climate regions. In the best case the solar power generated can cover up to 35% of the driving range per year. This contribution can vary by a factor of 2.5 between different climates, from 1800 to 5100 km annually, considerably mitigating the effect of ambient conditions on electric range. We propose developing consumer labels for solar electric vehicles that would consider this variation according to climatic conditions. The method described in this paper could help to frame initial discussions for such labels. We identify further requirements for research and development, standardisation, and policy needs. • Above 5000 km solar range possible for commuter car and van with integrated PV. • Ten year simulation reveals solar range differences by factor 2.5 across climates. • Over 44% difference in grid electricity needs across six climates globally. • At the moment vehicle integrated PV not financially viable. • Consumer labels for PVEV may be needed to inform about performance variations. [ABSTRACT FROM AUTHOR]

This article examines the effect of biodiesel blends on the exhaust aerosol from a Euro 3 passenger car. Five different feedstock oils (soybean, palm, sunflower, rapeseed, and used frying oil) were used to produce fuels with 10% vol. content in biodiesel (B10). Use of the B10 blends led to a systematic reduction of PM mass emissions in the range of ∼9% (rapeseed) to 23% (used frying oil) on average. The combination of particle size distributions based on the aerodynamic and the mobility diameters led to the estimation of the fractal dimension (DF) for non-volatile particles. This was found to range from 2.52 for the baseline (fossil) fuel to 2.62 for the palm oil blend, suggesting that biodiesel can affect the particle morphology, even at this low blending ratio. The differences were statistically significant. The increase of the DF is translated to more compact particle structure, which in turn denotes lower specific surface area. The volatile fraction of PM lies within a range of 1-9% when fossil diesel fuel is employed. Use of palm, sunflower and rapeseed B10 blends results to PM that contain up to 28% volatile particulate mass. The higher emissions of volatile components together with the lower specific area of non-volatile particles, promotes the formation of volatile particles, especially at high speed conditions. This increases the total particle population under motorway driving by up to three times over the baseline levels. [ABSTRACT FROM AUTHOR]

• Formalizing heterogeneity of the vehicle-driver system. • Free-flow term of a CF model leads to the formation and propagation of oscillations. • Simulations reproduce periodical oscillations with variable amplitudes and periods. • The concave growth pattern of the standard deviation of the speed is observed. • Validation was performed on three real-world car-following datasets. • The proposed approach provides accurate fuel consumption estimations. Road traffic congestion is the result of various phenomena often of random nature and not directly observable with empirical experiments. This makes it difficult to clearly understand the empirically observed traffic instabilities. The vehicles' acceleration/deceleration patterns are known to trigger instabilities in the traffic flow under congestion. It has been empirically observed that free-flow pockets or voids may arise when there is a difference in the speeds and the spacing between the follower and the leader increases. During these moments, the trajectory is dictated mainly by the characteristics of the vehicle and the behaviour of the driver and not by the interactions with the leader. Voids have been identified as triggers for instabilities in both macro and micro level, which influence traffic externalities such as fuel consumption and emissions. In the literature, such behaviour is usually reproduced by injecting noise to the results of car-following models in order to create fluctuations in the instantaneous vehicles' acceleration. This paper proposes a novel car-following approach that takes as input the driver and the vehicle characteristics and explicitly reproduces the impact of the vehicle dynamics and the driver's behaviour by adopting the Microsimulation Free-flow aCceleration (MFC) model. The congested part of the model corresponds to the Lagrangian discretization of the LWR model and guarantees a full consistency at the macroscopic scale with congested waves propagating accordingly to the first-order traffic flow theory. By introducing naturalistic variation in the driving styles (timid and aggressive drivers) and the vehicle characteristics (specification from different vehicle models), the proposed model can reproduce realistic traffic flow oscillations, similar to those observed empirically. An advantage of the proposed model is that it does not require the injection of any noise in the instantaneous vehicle accelerations. The proposed methodology has been tested by studying a) the traffic flow oscillations produced by the model in a one-lane road uphill simulation scenario, b) the ability of the model to reproduce car-following instabilities observed in three car-following trajectory datasets and c) the ability of the model to produce realistic fuel consumption estimates. The results prove the robustness of the proposed model and the ability to describe traffic flow oscillations as a consequence of the combination of driving style and vehicle's technical specifications. [ABSTRACT FROM AUTHOR]

The interest on the impact of vehicle automation and connectivity in the future road transport networks is very high, both from a research and a policy perspective. Results in the literature show that many of the anticipated advantages of connected and automated vehicles or automated vehicles without connectivity (CAVs and AVs respectively) on congestion and energy consumption are questionable. Some studies provide quantitative answers to the above questions through microsimulation but they systematically ignore the realistic simulation of vehicle dynamics, driver behaviour or instantaneous emissions estimates, mostly due to the overall increased complexity of the transport systems and the need for low computational demand on large-scale simulations. However, recent studies question the capability of common car-following models to produce realistic vehicle dynamics or driving behaviour, which directly impacts emissions estimations as well. This work presents a microsimulation study that contributes on the topic, using a scenario-based approach to give insights regarding the impact of CAVs and AVs on the evolution of emissions over a highway network. The motivation here is to answer whether the different driving behaviours produce significant differences in emissions during rush hours, and how significant is the impact of detailed vehicle dynamics simulation and instantaneous emissions in the outcome. The status of the network is assessed in terms of flow and speed. Furthermore, emissions are estimated using both the average-speed EMEP/EEA fuel consumption factors and a generic version of the European Commission's CO 2 MPAS model that provides instantaneous fuel consumption estimates. The simulation results of this work show that AVs can deteriorate the status of the network, and that connectivity is the key for improved traffic flow. Emissions-wise, the AVs have the highest fuel consumption per km travelled among other types, while CAVs only marginally lower the overall consumption of human-driven vehicles. For the same traffic demand, the total emissions for different vehicle types remain at comparable levels. • Traditional car-following models provide overestimated instantaneous acceleration values. • AVs do not facilitate Traffic Flow, and generate the highest emissions values per kilometer. • CAVs increase the capacity of the network and therefore during peak hours, they generate more emissions in absolute values. • In total, the differences in emissions per kilometre driven between CVs, AVs, CAVs do not exceed 6%. • Results show that the use of vehicle dynamics-based modelling in microsimulation (i.e. MFC free-flow model) is in cases, essential. [ABSTRACT FROM AUTHOR]

Tailpipe emissions of a pool of 13 Euro 6b light-duty vehicles (eight diesel and five gasoline-powered) were measured over an extensive experimental campaign that included laboratory (chassis dynamometer), and on-road tests (using a portable emissions measurement system). The New European Driving Cycle (NEDC) and the Worldwide harmonised Light-duty vehicles Test Cycle (WLTC) were driven in the laboratory following standard and extended testing procedures (such as low temperatures, use of auxiliaries, modified speed trace). On-road tests were conducted in real traffic conditions, within and outside the boundary conditions of the regulated European Real-Driving Emissions (RDE) test. Nitrogen oxides (NOX), particle number (PN), carbon monoxide (CO), total hydrocarbons (HC), and carbon dioxide (CO2) emission factors were developed considering the whole cycles, their sub-cycles, and the first 300 s of each test to assess the cold start effect. Despite complying with the NEDC type approval NOX limit, diesel vehicles emitted, on average, over the WLTC and the RDE 2.1 and 6.7 times more than the standard limit, respectively. Diesel vehicles equipped with only a Lean NOX trap (LNT) averaged six and two times more emissions over the WLTC and the RDE, respectively, than diesel vehicles equipped with a selective catalytic reduction (SCR) catalyst. Gasoline vehicles with direct injection (GDI) emitted eight times more NOX than those with port fuel injection (PFI) on RDE tests. Large NOX emissions on the urban section were also recorded for GDIs (122 mg/km). Diesel particle filters were mounted on all diesel vehicles, resulting in low particle number emission (~1010 #/km) over all testing conditions including low temperature and high dynamicity. GDIs (~1012 #/km) and PFIs (~1011 #/km) had PN emissions that were, on average, two and one order of magnitude higher than for diesel vehicles, respectively, with significant contribution from the cold start. PFIs yielded high CO emission factors under high load operation reaching on average 2.2 g/km and 3.8 g/km on WLTC extra-high and RDE motorway, respectively. The average on-road CO2 emissions were ~33% and 41% higher than the declared CO2 emissions at type-approval for diesel and gasoline vehicles, respectively. The use of auxiliaries (AC and lights on) over the NEDC led to an increase of ~20% of CO2 emissions for both diesel and gasoline vehicles. Results for NOX, CO and CO2 were used to derive average on-road emission factors that are in good agreement with the emission factors proposed by the EMEP/EEA guidebook. [ABSTRACT FROM AUTHOR]