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In this research, field slab samples were taken from an asphalt pavement in a hot climate with a design life of 40 years at 2, 4, and 7 years of pavement age to determine aging behavior with time at different depths. The asphalt binders were extracted and recovered to evaluate the aging and fatigue performance of the intermediate layer of the asphalt pavement. The chemical and rheological aging properties of the binders were evaluated using Fourier transform infrared spectroscopy and a dynamic shear rheometer, respectively. The pavement included 25 mm (1 in.) open-graded and 75 mm (2 in.) polymer-modified layers over three intermediate layer lifts. The intermediate layer aging is mostly governed by the connecting air voids and binder content of the asphalt mixes. The variation in aging deeper than 100 mm (4 in.) below the pavement surface was minor because of the absence of heat and access to air, with similar aging parameter values observed for different years of field sampling indicating little to no aging after construction. A good correlation ( R2 values of 0.79–0.92) was observed between the chemical property (carbonyl index) and rheological properties of the extracted binder for the dense-graded asphalt concrete layers between 25 and 100 mm depths. The fatigue performance of these extracted binders was evaluated by performing linear amplitude sweep tests. The results indicate that binder fatigue performance initially improved with moderate levels of aging but started to decline under extreme aging conditions.

California has a diverse climate that ranges from desert regions with some of the hottest places in North America to coastal regions with mild climates and cold summers. The selection of the binder's performance grade (PG) in California is based on a climate map that was developed in 2005 using 1960 to 1990 data from the National Climate Data Center (NCDC) analyzed using the Enhanced Integrated Climate Model (EICM) and the Long-Term Pavement Performance (LTPPBind 2.0) software. Climate change is happening all around the world, and California is no exception. Based on observed pavement performance, there was a need to revise the PG map using updated climatic data from various sources. In this study, the PG binder map for California was updated to better predict pavement performance using the latest available weather data. Thirty years of climate data (1991-2019) were considered to update the current binder's PG map. The weather data were collected from two main sources: NCDC and Modern-Era Retrospective Analysis for Research and Applications (MERRA). It was found that pavement structure types and thermal coefficients have insignificant effects on the binder performance grade. Also, it is recommended that the binder high PG for the central valley of California be changed based on the results obtained from analysis using EICM and LTPPBind Online.

Procurement of more environmentally sustainable materials for civil infrastructure can be supported using environmental product declarations (EPDs). An EPD is a standardized label that is a scientifically sound way to communicate the potential environmental impacts and selected resource use and waste production flows from all or part of the life cycle of a product. To be called a Type III EPD, the life cycle assessment (LCA) for products used in civil infrastructure must be performed in accordance with ISO standards and the relevant product category rule (PCR) for the product type. Most EPDs for civil infrastructure materials in North America are “cradle-to-gate”, i.e., they include the impacts from the extraction of raw materials from the earth and end at the point at which the product is ready to leave the gate of the last manufacturing location. The steps leading to publication of an EPD include: 1) Developing the PCR, 2) Developing the LCA for the EPD, 3) Creating the EPD, and 4) Verification and publishing of the EPD. Industry-average, regional-average, product-specific, and facility-specific EPDs—with differing specificity to a particular product—are used for different purposes. EPDs are a source of data for materials impacts for use in assessment of the complete life cycle. They provide information to identify changes in impacts that can be made early in the materials production. They also can be used to help procure lower impact materials. This white paper discusses benefits of using EPDs and makes recommendations for improving their validity. Several areas needing improvement in current use in procurement are identified and recommendations are presented for improving the use of cradle-to-gate EPDs in transport infrastructure construction materials procurement and to provide input to complete life cycle pavement LCA to support decision-making.View the NCST Project Webpage

Using post-consumer carpet calcium carbonate (PC4) in concrete can support a circular economy. Three treatments were evaluated to engineer PC4: furnacing at 600°C, furnacing at 900°C, and milling. Specimens were made with 5 and 15% PC4 replacement for Portland cement and were compared to controls with limestone filler replacement and with only Portland cement. Mortars with PC4 treated at 600°C exhibited 28-day compressive strength comparable to controls. X-ray diffraction and Fourier-transform infrared spectroscopyR show heat treatments led to compositional shifts and removal of polymers. Cumulatively, heat treatments can improve the characteristics of PC4 and could benefit both waste utilization and concrete production.

The California Department of Transportation (Caltrans) has been using full-depth recycling (FDR) as a pavement rehabilitation strategy since 2001. Early projects were recycled with foamed asphalt and cement. Cement-only treatments were permitted from 2015 to improve the properties of more marginal materials. However, shrinkage cracking associated with the hydration and curing of the cement-treated layers remains a concern, especially with regard to crack reflection through asphalt concrete surfacings and the related problems caused by water ingress.Crack mitigation has been studied for decades, and a range of measures related to improved mix designs and construction practices have been implemented by road agencies. One of the most promising measures, used in conjunction with appropriate mix designs, is that of microcracking the cement-treated layer between 48 and 72 hours after construction. In theory, this action creates a fine network of cracks in the layer that limit or prevent the wider and more severe block cracks typical of cement-treated layers. Limited research to assess microcracking as a crack mitigation measure has been completed on a number of projects in Texas, Utah, and New Hampshire. Recommendations from these studies were first implemented by the Texas Department of Transportation and then later by other state departments of transportation. However, longer-term monitoring on a range of projects in Texas, California, and other states had revealed that microcracking has not always been successful in preventing cracking. Some projects showed reflected transverse and block cracks in a relatively short time period, attributable to a number of factors including but not limited to cement content, cement spreading, the method of curing, and the interval between base construction and placement of surfacing.Discussions with researchers in Texas indicated that additional research was necessary to better understand the microcracking mechanism, and to identify the key factors influencing performance, including but not limited to aggregate properties, cement content, the time period before microcracking starts, layer moisture contents, roller weights and vibration settings, the number of roller passes, the field test methods and criteria used to assess the degree of microcracking, and the effects of early opening to traffic. A multiphase project was therefore initiated at the University of California Pavement Research Center (UCPRC) to investigate these outstanding issues. The second phase of this study is discussed in this report. This phase covered the design, construction, monitoring, and associated laboratory testing of a 37-cell test road to evaluate shrinkage crack mitigation procedures. The study found that microcracking is an effective mitigation measure, provided that design strengths do not exceed 600 psi (4.1 MPa) and that microcracking is done between 48 and 56 hours after compacting the layer.

The aging of asphalt concrete is mainly governed by the aging of the asphalt binder, which is a naturally occurring organic hydrocarbon. Both chemical and rheological properties of asphalt binder are expected to change as aging continues. The pavement industry is increasing the use of different recycled materials in the construction and rehabilitation of flexible pavements to preserve natural resources, save costs, and reduce environmental emissions. The aged binder from recycled materials is expected to alter the binder properties and its aging characteristics in the new mix. In this study, 3 different virgin base binder types (PG 64-16, PG 58-22, and PG 70-10) and 7 different binder blends containing recycled binders (up to 100 % binder replacement) were subjected to different aging conditions. The rheological and chemical properties of these binders were characterized using a dynamic shear rheometer and Fourier transform infrared spectroscopy, respectively. It was found that the Glover-Rowe parameter distinctively captured the change in binder rheological properties with aging for the different binder blends. A good correlation (R2value of 0.83-1.00) was observed between binder chemical and rheological properties. The source and performance grade of the base binder were found to govern the correlation between the rheological and chemical properties of the blended binder. Hamburg wheel tracking (for rutting and moisture sensitivity) and indirect tensile asphalt cracking test (for fracture) tests were conducted on asphalt mixes maintaining the same blended binder ratios. The laboratory mix performance parameters were found to correlate well with the properties of the blended binders. Therefore, properties of the blended binders can be an important source of information for predicting the performance of asphalt mixes containing recycled materials.

Weigh-in-motion (WIM) devices measure and record highway vehicle axle loads. The data they collect include axle loads and spacing, vehicle classification and gross weights, and travel speed. These WIM data are used for pavement design, management, and performance studies. In 2016, there were 123 WIM devices operating on sites throughout the California state-owned highway network, one of the densest and best maintained in the United States. The University of California Pavement Research Center (UCPRC) has studied California’s WIM data with the California Department of Transportation (Caltrans) since 2007 to advance mechanistic-empirical (ME) pavement design procedures. Previously, the UCPRC completed the first analysis of the WIM data collected from 1998 to 2003 to discover similarities in axle load distributions at the WIM sites and then grouped them using cluster analysis to generate default traffic inputs for pavement design software. For this research, the UCPRC processed WIM data collected from 80 California WIM-measuring sites from 2004 to 2015, identified the axle load distribution for each site, and updated the earlier grouping using hierarchical cluster analysis. A decision tree was developed to classify WIM data into five WIM axle load spectra, which have been implemented in the Caltrans pavement management system database, PaveM, to generate truck traffic inputs in the CalME and Mechanistic-Empirical Pavement Design Guide (MEPDG) pavement design software tools used by Caltrans for asphalt and concrete pavement design, respectively.

In late 2015, Caltrans requested that 26 recently constructed concrete projects be tested for smoothness in terms of the International Roughness Index (IRI). The stated purpose was to observe measured IRI on projects accepted after a standard special provision (SSP) change that Caltrans made in 2013 and that was incorporated into the 2015 Construction Contract Standards. The projects provided 52 test sections for evaluation, consisting of three types of paving work: (1) diamond grind on existing pavement, (2) new continuously reinforced concrete pavement, and (3) new jointed plain concrete pavement. The project plans had completion dates from May 2010 to December 2014, and contract acceptance dates from April 2014 to October 2015. Caltrans did not identify which projects had the new SSP or specification change in its contract documents. The IRI data were collected from October 2016 to December of 2016. The IRI data collected included the effects of paving, any corrective grinding required to meet contract acceptance, and the increased roughness caused by traffic over post-construction periods of one to more than two and a half years. At the time of testing in 2016, the UCPRC test vehicle was equipped with a point laser in the left wheel path and a wide spot laser in the right wheel path. The data presented in this technical memorandum are primarily from the wide spot laser because the current standards require the wide spot laser. In general, the IRI measured by a point laser can be unduly increased due to the surface texture of the pavement, which is part of the reason for moving toward a wide spot laser. The construction specification considers both wheel paths and not just the right wheel path tested in this project. The IRI data using the wide spot laser in the right wheel path alone showed that 22% of the 0.1 mi. long sections met the construction standard of 60 in./mi. when measured one to two and a half years after construction. Based on the results from the right wheel path and the wide spot laser, 67% of the right wheel path sections are in good condition with IRI values between 60 and 94 in./mi., 28% are in acceptable condition with IRI values between 95 and 170 in./mi., and 5% are in poor condition with IRI values of 170 in./mi. or greater. Although Caltrans did not identify which projects included the new specification, a trend was observed that projects completed later had lower IRI values than those completed several years earlier.

“Complete streets” is a design concept for primarily urban streets and intersections (existing and/or new) intended to encourage active transportation by bicyclists and pedestrians by making streets safer, convenient, and attractive for active transportation; motorized transportation and parking are also accommodated in the design concept. The social and economic performance indicators included in the social life cycle assessment (SLCA) framework that was used in this project provide a great deal of insight into specific and different potential benefits of a given complete streets project. The SLCA framework is based on five categories of concerns and 17 performance measures or indicators. The indicators were tested in the project and evaluated for final recommendations for use in future studies. The results are compared with the existing streets that were configured to be vehicle-centric. The case studies were solicited in more and less advantaged neighborhoods so that the framework could also be evaluated in different contexts. Use of the CalEnviroScreen tool from the California Environmental Protection Agency was also investigated to assess the exposure of neighborhoods and their vulnerability to environmental impacts in conjunction with the performance indicators when evaluating the potential benefits for disadvantaged neighborhoods (also called priority population areas). As was found in the preceding study, the primary environmental impacts come from the use stage, namely changes in vehicle travel and changes in vehicle speeds from complete street design features. Recommendations are made for dropping some indicators because of difficulties collecting data or interpreting the results, modifications of other indicators, and adding some new indicators to fill important gaps.View the NCST Project Webpage

Spurred in part by state-level climate policies, California cities and counties have released climate action plans (CAPs) over the last decade to set emissions reduction targets and outline actions that will help meet those goals. However, the state provides little guidance to jurisdictions on how to produce these plans. The range of information included in CAPs varies dramatically across jurisdictions. Additionally, little is known about how jurisdictions transition from the planning to the implementation phase of climate action, or what major factors influence their decision-making process. Other state laws promote emissions reductions in disadvantaged communities, highlighting the importance of making equity a key consideration in CAPs.Researchers at the University of California, Davis assessed and scored over 30 CAPs released between 2009 and 2020 based on the degree to which they addressed three themes: emissions reductions, cost, and equity. The researchers also surveyed local agency staff from 25 California jurisdictions with published CAPs about the importance of different factors during climate action planning and implementation, the inclusion of equity impacts in CAPs, sources of funding, and more. Finally, the researchers developed a set of guiding questions to assist jurisdictions in developing CAPs that include equity considerations both broadly and by specific sector. This policy brief summarizes the findings from that research and provides policy implications.View the NCST Project Webpage

California state government has established a series of mandated targets for reducing the greenhouse gas (GHG) emissions that contribute to climate change. With a multiplicity of emissions sources and economic sectors, it is clear that no single change the state can make will enable it to achieve the ambitious goals set by executive orders and legislation. Instead, many actors within the state’s economy—including state agencies such as the California Department of Transportation (Caltrans)—must make multiple changes to their own internal operations. The focus of this study and technical memorandum is to examine several strategic options that Caltrans could adopt to lower its GHG emissions in operating the California (CA) state highway network and other transportation assets so it can help meet the state’s GHG reduction goals. Although many GHG reduction strategies appear to be attractive, simple, and effective, most also have limitations, trade-offs, and unintended consequences that cannot be identified without a preliminary identification and examination of the full system they operate in and their full life cycle. To achieve the most rapid and cost-effective changes possible, the costs, times to implement, and difficulty of implementation should also be considered when the alternative strategies are being prioritized. This project first developed an emissions reduction “supply curve” framework by using life cycle assessment (LCA) to evaluate full-system life cycle environmental impacts and life cycle cost analysis (LCCA) to prioritize the alternative GHG-reduction strategies based on benefit and cost. This framework was then applied to an example set of strategies and cases for Caltrans operations. This technical memorandum presents the results of the supply curve framework’s development and its application to six strategies for changing several Caltrans operations identified by the research team. The six strategies were: (1) pavement roughness and maintenance prioritization, (2) energy harvesting using piezoelectric technology, (3) automation of bridge tolling systems, (4) increased use of reclaimed asphalt pavement, (5) alternative fuel technologies for the Caltrans vehicle fleet, and (6) solar and wind energy production on state right-of-ways. A summary of the methodology and the resulting supply curve that includes all the strategies considered and ranked is published in a separate white paper. This technical memorandum provides the details, assumptions, calculation methods, and results of the development of the GHG reduction supply curve for each strategy. Although this current study’s scope is limited to development of a supply curve for GHG emissions only, there are plans to expand the study’s scope to include other environmental impacts and to develop supply curves for them as well.

Historically, rubberized and non-rubberized open-graded friction courses (OGFCs) have been placed to provide three benefits: to increase traffic safety, to reduce urban highway noise, and to preserve the surface of the main pavement structural section. However, stringent environmental regulations on stormwater runoff management enacted recently have forced transportation agencies with limited right of ways in urban areas to search for creative methods to treat runoff and receive credits for preventing pollution from highways. This literature review was undertaken to explore ways to optimize current RHMA-O mix designs to provide multifunctional benefits, including water quality treatment. The literature review showed that permeability measurement is an essential parameter that influences a wide range of OG (both rubberized and non-rubberized) pavements’ performance. Further, current Caltrans aggregate gradations contain a larger fraction of fine aggregate sizes and this may also influence the permeability and functional performance of RHMA-O pavements. Part of this literature review includes an action plan recommending that the next phase of this work include optimizing current Caltrans mix designs and the mix design procedure in the laboratory and undertaking subsequent field investigations.

Local governments increasingly prepare Climate Action Plans to lay out specific strategies for achieving local and state greenhouse gas reduction goals. Strategies to reduce transportation emissions are often a key component of these plans, as the transportation sector is responsible for 41% of greenhouse gas emissions in California and 28% in the US. However, many Climate Action Plans do not quantify the emissions reductions or costs of proposed strategies, and even fewer consider the life cycle impacts of the strategies. Life cycle-based assessments consider emissions and costs that occur at the outset of a strategy’s implementation (e.g., purchase, installation, and construction), during operation and maintenance, and at end-of-life. Quantifying the life cycle cost effectiveness and emissions reductions of different strategies can, along with other community priorities, inform the design and implementation of Climate Action Plans that achieve climate goals at a reasonable cost. A marginal abatement cost curve is a useful way to present this information, offering a visualization of the rank order cost-effectiveness and total possible emissions reductions of alternative strategies in a Climate Action Plan.Researchers at the University of California, Davis developed a decision support framework for local governments to assess life cycle greenhouse gas reductions and costs of Climate Action Plan strategies. The researchers demonstrated their approach by developing marginal abatement cost curves for two California counties, Yolo and Unincorporated Los Angeles, based on strategies from their respective Climate Action Plans. This policy brief summarizes findings from that research.View the NCST Project Webpage

The University of California Pavement Research Center and the Interlocking Concrete Pavement Institute worked with partners in the concrete and asphalt pavement industries and Tongji University to organize a workshop in November 2017 with the goals of identifying knowledge, information, and communication barriers to adoption of permeable pavement of all types, and then creating a road map to address and overcome them. The workshop brought together stakeholders from the planning, stormwater quality, flood control, and pavement communities to listen to presentations, exchange ideas, discuss unanswered questions identified by the group, and develop a proposed road map to fill the gaps in knowledge, processes, and guidance. Participants represented local, state and federal government, consultants, non-governmental organizations, contractors/ material producers, and academia. The road map produced from the discussions is built around “routes” of proposed actions to remove technical and institutional barriers to realize the goal of making permeable pavements a fully viable alternative in standard practice.View the NCST Project Webpage

More than 90 percent of the road and highway network in the United States is paved with asphalt concrete. Maintenance and periodic rehabilitation require a continuous supply of aggregates and asphalt binder, both of which are becoming increasingly scarce and expensive. Recycling and reusing these resources can reduce costs and improve sustainability. The most common recyclable material used in road construction is reclaimed asphalt pavement (RAP), which is milled asphalt surface layers that have been removed from existing pavements before new asphalt overlay is placed. Reclaimed asphalt roofing shingles (RAS) are another potential source of asphalt binder.There is growing interest in allowing significantly higher percentages of RAP and RAS in asphalt mixes used on state and local roadways. However, making this change has raised concerns regarding how these composite binders may influence the performance and durability of asphalt mixes, depending on the blends of different virgin and reused binders. Researchers at the UC Pavement Research Center investigated the use of higher percentages of RAP and RAS as a partial replacement for the virgin binder in new asphalt mixes and their effect on pavement performance in California. This research brief summarizes findings from that study.View the NCST Project Webpage

Streets, sidewalks, parking areas, plazas, and other paved surfaces cover large portions of urban areas. These urban hardscapes contribute significantly to cities’ resource consumption. Although urban hardscapes enable people and goods to move freely, they also have profound impacts on cities’ water, air quality, energy, and material use. Reducing the environmental impacts of hardscapes will be an important component of making cities more sustainable. The necessary first step is to quantify those impacts.UC Davis and Tongji University researchers developed a methodology that combines urban metabolism and life cycle assessment to examine the life cycle impacts of hardscapes at the urban scale rather than at the product or project scale. Urban metabolism (UM) is a method that accounts for the flow of resources such as energy, materials, and water into an urban area, their processing and consumption within the urban area, and their subsequent flows out of the area. Life cycle assessment (LCA) is a quantitative environmental assessment method that considers the total supply chain and life cycle impacts of a product or system from “cradle to grave.”View the NCST Project Webpage

A multitude of goals have been stated for complete streets including non-motorized travel safety, reduced costs and environmental burdens, and creation of more livable communities, or in other words, the creation of livable, sustainable and economically vibrant communities. A number of performance measures have been proposed to address these goals. Environmental life cycle assessment (LCA) quantifies the energy, resource use, and emissions to air, water and land for a product or a system using a systems approach. One gap that has been identified in current LCA impact indicators is lack of socio-economic indicators to complement the existing environmental indicators. To address the gaps in performance metrics, this project developed a framework for LCA of complete streets projects, including the development of socio-economic impact indicators that also consider equity. The environmental impacts of complete streets were evaluated using LCA information for a range of complete street typologies. A parametric sensitivity analysis approach was performed to evaluate the impacts of different levels of mode choice and trip change. Another critical question addressed was what are different social goals (economic, health, safety, etc.) that should be considered and how to consider equity in performance metrics for social goals. This project lays the foundation for the creation of guidelines for social and environmental LCAs for complete streets.View the NCST Project Webpage

Urban hardscapes can be defined as human-altered surfaces in contact with the earth in urban areas other than alterations for horticulture. Hardscape covers large portions of the urban surface area, and has potentially large influence on air emissions, truck traffic and its associated problems, and the potential for flooding. Modeling the inflows of hardscape materials and the outflows of demolished hardscape and other rock-based products from buildings and other civil infrastructure is expected to provide a means to find solutions for reducing these flows and their impacts. Modeling of urban hydrology with respect to the effects of hardscape on surface and groundwater flows from precipitation is expected to provide a means to find solutions that will reduce the risk of flooding and improve groundwater recharge.The goal of this white paper is to advocate that researchers and policy-makers use the analytical approach of combining urban (UM), material flow analysis (MFA) and elements of life cycle assessment (LCA) to measure and improve the efficiency of urban hardscape in large urbanized areas with respect to environmental impacts affecting global warming, safety and quality of life through use of alternative hardscape structure and materials and more permeable hardscape. The white paper provides details on the proposed UM-LCA framework. Additionally, several data sources and modeling tools were identified that can be used in the UM-LCA framework to quantify material and energy flows and environmental impacts including water flows. An effort was also made to identify data for a few of the cities in California in order to demonstrate parts of the data collection and presentation process. The framework developed is not limited to a single U.S. state, rather it can be used in any geographic region of the U.S.View the NCST Project Webpage

One of the benefits of using mechanistic-empirical (ME) design methods for pavements is the ability to calculate pavement response to various loading and climate conditions, and then in turn to model the entire damage process that is expected to occur over the pavement lifetime. One property that is currently not accounted for within California’s ME design software (CalME) is the change in stiffness of unbound materials that may occur due to seasonal moisture patterns. The engineering properties of unbound material may change due to a variety of factors, such as fluctuations in water content, changes in suction during wetting or drying periods, changes in overburden stress, and they are also dependent on geologic setting. Before moving to develop and implement more complex relationships to model assumed changes in the properties of unbound layers due to seasonal moisture changes, the University of California Pavement Research Center (UCPRC) evaluated the extent of variation that is observed in the field. The goals of this research are to evaluate whether or not these speculated seasonal changes in unbound material properties warrant further design optimization, and if so, how research to characterize such optimization should proceed in the future.In this research, an experiment was performed to evaluate if noticeable changes in subgrade stiffness can be identified and explained using available, pertinent, and easy-to-use pavement monitoring equipment. Testing was performed twice on sections across California, once in the wet season and once in the dry season, to get a broad picture of the types of materials present and their corresponding properties during wet and dry seasons. Monitoring of a test section at UC Davis was also performed more frequently to observe changes in stiffness occurring after rainfall events and during wetting and drying cycles.The literature and various laboratory experiments investigating the influence of moisture and suction on the resilient response of unbound materials strongly suggest that a large degree of variability in stiffness should be encountered in different moisture conditions. However, the results of the study revealed that a majority of the unbound material tested experienced minor, if any, changes at all in stiffness between the two rounds of testing seasonal testing. The most susceptible materials to stiffness variation were not necessarily the compacted subgrade material, but were the stabilized and unstabilized granular materials directly underlying the asphalt surface. While changes in moisture content and penetration resistance were observed between the two rounds of testing, they did not necessarily correspond to significant fluctuation in the field-tested stiffness of the unbound materials; rather, other factors such as spatial variability, drainage conditions, soil type, and influences from overlying layers tended to have a much larger influence on the resilient response of these materials than did seasonal moisture change.It is therefore recommended that CalME’s current assumption of constant stiffness for unbound layers continue to be used, except in cases where the designer identifies issues with drainage, irrigation, or other likely causes of seasonal variation of stiffness. Performing FWD testing for backcalculation of unbound layer stiffnesses after the rainy season, or at other times of highest moisture contents where rainfall is not the main source of moisture, will impart some conservatism into designs. UC Pavement Research Center Research Report UCPRC-RR-2017-11

In early 2017, the University of California Pavement Research Center (UCPRC) and the National Center for Sustainable Transportation (NCST), working with the Interlocking Concrete Pavement Institute (ICPI), identified gaps in knowledge and other barriers to wider implementation that were perceived to be holding back the full potential for deployment of pavements that can simultaneously solve transportation, stormwater quality, and flood control problems. Further discussions were held with the National Ready Mixed Concrete Association (NRMCA), the National Asphalt Pavement Association (NAPA), and the Tongji University Sponge City Project (Shanghai, China). A workshop was organized in November 2017 based on those discussions with the goal of identifying knowledge, information, and communication barriers to adoption of permeable pavement of all types, and creation of a road map to address and overcome them. The workshop brought together a diverse group of stakeholders from the planning, stormwater quality, flood control, and pavement communities to hear listen to presentations, exchange and discuss unanswered questions identified by the group, and then to discuss a proposed road map to fill the gaps in knowledge, processes, and guidance. This document is the result of that workshop and additional development of the road map. It presents the organization of the workshop, summaries of the presentations and the breakout and plenary discussions, and the final road map developed from the results of the workshop.View the NCST Project Webpage

The freight system is a key component of California’s economy, but it is also a critical contributor to a number of externalities. Different public agencies, private sector stakeholders, and academia engaged in the development of the California Sustainable Freight Action Plan (CSFAP). This plan put forward a number of improvement strategies/policies. However, the freight system is so complex and multifaceted, with a great number of stakeholders, and freight operational patterns, that evaluating or assessing the potential impacts of such strategies/policies is a difficult task. To shed some light, this project develops a freight system conceptualization and impact assessment framework of the freight movements in the State. In doing this, the framework assesses the impact of commodity flows from different freight industry sectors along supply chains within, originating at, or with a destination in the state of California.The conceptual framework analyzes the freight flows in supply chains, and the type of freight activity movements and modes. The framework uses a Life Cycle Assessment (LCA) Methodology. The framework could be extended to support multidimensional cost/benefit appraisals for both direct benefits (e.g., delays, costs, accidents, maintenance) and social benefits to non-users which include impacts on regional and national economies as well as environmental and health impacts. This report discusses the main components of the conceptual framework based on a comprehensive review of existing methodologies. The implementation is limited to the Life Cycle Impact Assessment (LCIA) following the Environmental Protection Agency’s Tool for Reduction and Assessment of Chemicals and Other Environmental Impacts (TRACI).The report describes the results from the LCIA implementation for a number of case studies. Specifically, the work estimated the impacts of moving a ton of cargo over a mile for various industry categories and commodity types. These results show the relative difference across industries and commodities and could serve to identify freight efficiency improvement measures in the state of California.View the NCST Project Webpage

This technical memorandum provides additional information regarding smoothness on several thin asphalt overlay projects constructed soon after changes in Caltrans specifications for constructed pavement surfaces using the International Roughness Index (IRI) as the quality metric. The IRI data were collecting using inertial profilers, before and after construction, on overlaid surfaces employing one of three repairs—digouts, cold in-place recycling (CIR), mill and filling—or none. Because the data were collected after the close of the construction contract, they include the effects of any grinding that Caltrans required the contractor to perform prior to that close. However, the data provide a preliminary look at whether changes in the construction smoothness specification necessitate changes to any of the recommendations in a previous report regarding repairs before overlay. The results indicate that the recommendations in the previous report are generally being followed. The results also indicate that the previous recommendation to not include milling before overlay when IRI is less than 120 inches/mile or below 95 inches/mile may need to be revised under the new specification. However, additional data are needed, since only two projects with milling were included in this data set. A survey of district practices conducted in September 2017 indicated that decisions regarding the inclusion of digouts, milling, and CIR prior to overlay were based on addressing load-related cracking, not roughness. It was observed that decisions regarding pre-overlay repairs for the small set of projects reviewed have generally resulted in smoother existing pavements not being subjected to pre-overlay repairs, and digouts, milling, and CIR being used on successively rougher existing pavements.

The main purpose of the project is to improve the ability of Caltrans pavement designers to use mechanistic-empirical (ME) pavement design procedures that were developed and calibrated for California conditions as part of Partnered Pavement Research Center Strategic Plan Element (PPRC SPE) 4.1 and refined in SPE 3.4. Specifically this project is part of a long-term series of tasks to collect regional materials data for use by Caltrans in ME flexible pavement designs and rehabilitations. This technical memorandum documents the current state of the Standard Materials Library (SML) for CalME, the ME analysis and design computer program for flexible pavements developed by the UCPRC for Caltrans. This technical memorandum summarizes the role of the SML in the ME design process, the classifications of different pavement materials, the relevant models applicable to each material group, and the processes for identifying various model parameters. The technical memorandum also describes how construction variabilities are accounted for in the SML. A full list of materials included in the SML at the completion of this task in 2014 is presented, including the research conducted up to that time on the materials and how their model parameters were determined.

Falling head permeability tests were conducted on seven projects, four with dense-graded hot mix asphalt surfaces and three with gap-graded rubberized hot mix asphalt surfaces. Tests were conducted between the two wheelpaths and in the right wheelpath, and in both directions of traffic. Averaging all the test results shows that the permeability of RHMA-G is much greater than that of HMA: 2.9E-3 cm/sec versus 6.1E-4 cm/sec, respectively. However, one of the three projects with a gap-graded rubberized hot mix asphalt surface had permeabilities not consistent with the other two. When data from that gap-graded rubberized hot mix asphalt surface was removed, the average value for the surface permeability dropped over 80 percent, to 4.2E-4 cm/sec. This average is lower than the average permeability for dense-graded hot mix asphalt, and the data remaining from the six projects—four dense-graded and two gap-graded—showed no statistical difference in the average surface permeability of HMA and RHMA-G when tested at the 95% confidence level. On four of the seven projects, including all three of the RHMA-G sections, testing in both directions and in both wheelpaths locations showed no statistical difference in surface permeability. But, one HMA project showed dissimilarity in both directions and in the wheelpaths. Five pairs of cores from this project were then tested for permeability and specific gravity in the laboratory. Unfortunately, no conclusions could be drawn due to a lack of spatial information; however one of the five locations had very little variability between core pairs in either specific gravity or permeability, while another location had significant differences between the specific gravity and permeability measurements. When data from this dense-graded hot mix asphalt surface were removed along with the data from the one gap-graded rubberized hot mix asphalt surface with very high permeability, the remaining five projects—three dense-graded and two gap-graded—again showed no statistical difference in the average surface permeability of HMA (3.3E-4 cm/sec) and RHMA-G (4.2E-4 cm/sec) when tested at the 95% confidence level. It is recommended that testing of more RHMA-G mixes may be warranted to see if the high permeability on one mix in this study is unique. Construction QC/QA should also be examined to see if that mix met compaction specifications.

Raising the albedo (solar reflectance) of streets can lower outside air temperature, reduce building energy use, and improve air quality in cities. However, the production and installation of pavement maintenance and rehabilitation treatments with enhanced albedo (“cool” pavements) may entail more or less energy consumption and carbon emission than that of less-reflective treatments. We developed several case studies in which a cool surface treatment is substituted for a more typical treatment (that is, a cool technology is selected instead of a more typical technology). We then assessed over a 50-year analysis period the changes in primary energy demand (PED, excluding feedstock energy) and global warming potential (GWP, meaning carbon dioxide equivalent) in Los Angeles and Fresno, California. The analysis considers two stages of the pavement life cycle: materials and construction (MAC), comprising material production, transport, and construction; and use, scoped as the influence of pavement albedo on cooling, heating, and lighting energy consumption in buildings. In Los Angeles, substituting a styrene acrylate reflective coating or a chip seal for a slurry seal in routine maintenance, or a bonded concrete overlay on asphalt (BCOA) without supplementary cementitious materials (SCM) for mill-and-fill asphalt concrete in conventional or long-life rehabilitation, induced MAC-stage PED and GWP penalties that substantially exceeded use-stage savings, primarily due to material production. Modified rehabilitation cases in which SCM comprised 21% to 50% of the BCOA's total cementitious content by mass (portland cement + SCM) yielded smaller total (MAC + use) PED and GWP penalties, or even total PED and GWP savings. Trends in Fresno were similar, with some differences in GWP outcomes that result from Fresno's longer heating season. The modified rehabilitation cases using BCOA with high SCM content yielded total GWP savings in each city; all other cases yielded total GWP penalties. The magnitude of the one-time GWP offset offered by global cooling from the increased albedo itself always, and sometimes greatly, exceeded the 50-year total GWP penalty or savings. In Los Angeles, the annual building conditioning (cooling + heating) PED and energy cost savings intensities yielded by cool pavements were each about an order of magnitude smaller than the corresponding savings from cool roofs.

Neoclassical economists posted many mea culpas after they completely missed the Financial Crisis of 2008. Some heterodox schools of thought, however, claimed to have seen it coming. Among these were the Austrians and Post Keynesians. There was a surge in references to Austrian Business Cycle Theory in both the scholarly and popular press, while Post Keynesians like Steve Keen took to the blogosphere to warn people of the coming crash. One is led to wonder, however, if both can truly lay a legitimate claim to such accurate precognition when their theoretical underpinnings are so radically different? Can it be that deviations of the actual from the "natural" rate of interest were to blame at the same time that Keynes/Kalecki-style boom-bust cycles were emerging? To answer this question, an empirical test is run comparing the explanatory power of models based on each theory. Rather than limit this to just the period around the Financial Crisis, the test covers 1962 through 2020. The overall results are then compared, as well as the fit just leading up to and through the recession of 2008Q1 to 2009Q2. The results suggest that the Post Keynesians have a considerably stronger case than the Austrians. [ABSTRACT FROM AUTHOR]

The application of asphalt overlays comprises a significant percentage of the maintenance activities undertaken to improve the condition of existing asphalt pavements, and greater attention is now being paid to improving surface smoothness by constructing smoother overlays. The expected benefits of smoother overlays include longer service life due to decreased dynamic loading, improved fuel economy, and greater road-user comfort. In this study, data from the California Department of Transportation (Caltrans) Pavement Condition Survey (PCS) for projects built between 2000 and 2009 were used to investigate the effects of repairs, pavement pre-overlay smoothness (in terms of International Roughness Index, IRI), overlay mix type (dense-graded, gap-graded, open-graded), and binder type (rubberized versus conventional or polymer-modified) on initial post-construction overlay smoothness. The results are based on overlays constructed prior to implementation of the Caltrans smoothness specification for overlay construction. Linear mixed effects models were used in the analysis to take into account the variation across random effect variables. In this study, overlay smoothness was measured in terms of IRI. The analysis results indicated that the pavement pre-overlay IRI was the most important variable affecting overlay smoothness: pavements with lower pre-overlay IRI were smoother than those with higher pre-overlay IRI. When the pre-overlay condition was poor, increasing overlay thickness was also found to have a significant effect on post-overlay smoothness. In terms of pre-overlay repairs, analysis of Caltrans PCS data showed that overlays were smoother when digouts (milling and patching in the wheelpaths) were performed compared with milling of the entire surface prior to the overlay. The effects of overlay mix type and binder type were dependent on the pre-existing pavement condition and/or other factors.

This memorandum summarizes the results of measurements of macrotexture on a set of Caltrans and local government pavement surface treatments, and the results of bicycle vibration measurements and a survey of bicycle ride quality on most of those sections. The work was performed to address concerns raised by local bicyclists regarding ride quality after a modified-binder seal coat (chip seal) was placed on State Route 1 in San Luis Obispo County (SLO-1). The test sections that were used for the bicycle vibration and ride quality measurements included various surface treatments on existing chip seals on State Route 198 in Monterey County (Mon-198), several locations on SLO-1, and on other state highway and county road sections in Yolo, Butte, El Dorado, Placer, Sonoma, Marin, and San Mateo counties. Macrotexture was measured in terms of mean profile depth (MPD). Three different test methods were used to measure MPD: the sand patch method and the laser texture scanner (LTS), which provide measurements on a small area at a single location (about 12 square inches [100 square cm]); and the inertial profiler (IP), which is mounted on a vehicle and provides a continuous measurement in the longitudinal direction. Also presented are statistical correlations between macrotexture, roughness (in terms of International Roughness Index [IRI]), bicycle vibration, and bicycle ride quality for the initial set of treatment sections surveyed, and modeling of the relationships between macrotexture, roughness, vibration, and perceived ride quality for bicyclists. Conclusions are presented regarding the MPD values measured on various road sections, including those built with two 3/8" aggregate gradation chip seal specifications (one coarser than the other), and the variability of MPD found between sections built using the coarser 3/8" aggregate grading. Conclusions are also presented regarding the three MPD measurement methods. Findings are presented regarding the MPD values from other types of treatments, including possible treatments to be placed on SLO-1 to address a bicycle ride quality issue. Results are also presented regarding the effects of trafficking on MPD values. Correlations between bicycle vibration and MPD are shown, and between MPD, IRI, bicycle vibration, and bicyclists’ perception of ride quality and pavement acceptability for use by bicycles. Recommendations are made regarding a range of MPD values that might be used to select chip seal specifications based on “acceptability” where bicycle ride quality is an issue, selection of remedial treatments for SLO-1 based on the Mon-198 test sections, naming conventions for chip seals, and the use of additional rolling to reduce the texture of chip seals built using the coarser 3/8" aggregate grading.