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Pavement maintenance activities are widely regarded to be critical elements during pavement life cycle, different maintenance techniques have been used to restore or extend the service lives of pavements. However, the existing maintenance practices on pavement system have problems that impair the economic benefits, disturb the natural environment, and somewhat ignore the needs from stakeholders. To minimize these negative impacts, sustainability is an ideal way because it addresses the problems under Triple Bottom Line (TBL, refers to economy, environment, and society). Sustainability analysis within transportation or pavement industry has been studied in different countries, but the concept of sustainable pavement maintenance is relatively new and has not been defined well yet. In this research, the concept of sustainable pavement maintenance has been proposed and defined to help benefit the current pavement industry. Rating tool has its advantages measuring sustainability activities. There are many rating tools designed for sustainable infrastructure, transportation, or pavement, but maintenance has its own characteristics and yet never had its own rating tool. To link the theoretical concept of sustainable pavement maintenance with actual projects, a sustainability rating tool for pavement maintenance (Pavement Sustainability Index for Maintenance, PSIM) has been developed by a so-called 5-step methodology. Step one and two are to determine the rating categories and indicators; step three is to determine the priority of each category by the Analytic Hierarchy Process (AHP); step four is to determine points distribution under each indicator by reviewing the sustainability practices of 8 State DOTs; final step is to propose the certification methodology according to the Pavement Sustainability Index (PSI) earned by the maintenance project. To prove the usability value of PSIM, four common maintenance activities have been discussed as case studies, including rejuvenation, utility cut restoration (UCR), overlay, as well as mill and overlay. The projects selected were located in or adjacent to Louisville, KY. Among the nine projects being evaluated by PSIM framework, UCR projects were not sustainable; rejuvenation project, overlay projects, and one of the mill and overlay projects earned one PSIM star; two PSIM stars were awarded to two of the mill and overlay projects.

The issue of effectively scheduling pavement maintenance and rehabilitation treatments over a multi-year planning horizon plagues road authorities around the world with the significance of this issue being amplified by both an ageing pavement network and the trend towards insufficient fund allocation. The scope of the problem can be quantified as follows: if only a single treatment is able to be applied to each individual road segment in a single year, then the total number of possible programmed maintenance and rehabilitation schedule alternatives for a moderate-sized network of 1,000 road segments, with eight different treatments possible, over a twenty year anaysis period is ((1.0 × 103)8)20 = 1.0 × 10480. Assuming that a computer can build and evaluate 100 complete maintenance and rehabilitation schedules a second, to identify the optimal schedule for this 1,000 segment road network would take 3.17 × 10471 years. The overall goal of this study is to investigate the benefits of applying modern heuristic optimisation techniques to the problem of pavement main- tenance and rehabilitation scheduling over a multi-year planning horizon. To address this goal, a four stage approach was utilised using a real road network with real pavement condition data as the test benchmark.

This dissertation presents a methodology for the joint optimization of a variety of pavement construction and management activities for segment and system problems under multiple budget constraints. The objective of pavement management is to minimize the total discounted life time costs for the agency and the highway users by finding optimal policies. The scope of the dissertation is focused on continuous time and continuous state formulations of pavement condition. We use a history-dependent pavement deterioration model to account for the influence of history on the deterioration rate. Three topics, representing different aspects of the problem are covered in the dissertation. In the first part, the subject is the joint optimization of pavement design, maintenance and rehabilitation (M&R) strategies for the segment-level problem. A combination of analytical and numerical tools is proposed to solve the problem. In the second part of the dissertation, we present a methodology for the joint optimization of pavement maintenance, rehabilitation and reconstruction (MR&R) activities for the segment-level problem. The majority of existing Pavement Management Systems (PMS) do not optimize reconstruction jointly with maintenance and rehabilitation policies. We show that not accounting for reconstruction in maintenance and rehabilitation planning results in suboptimal policies for pavements undergoing cumulative damage in the underlying layers (base, sub-base or subgrade). We propose dynamic programming solutions using an augmented state which includes current surface condition and age. In the third part, we propose a methodology for the joint optimization of rehabilitation and reconstruction activities for heterogeneous pavement systems under multiple budget constraints. Within a bottom-up solution approach, Genetic Algorithm (GA) is adopted. The complexity of the algorithm is polynomial in the size of the system and the policy-related parameters.

Sustainability is increasingly becoming a significant part of strategic asset management worldwide. Road agencies are providing guidelines to assess the relative sustainability of road projects. Unfortunately, environmental features of a road project are still considered as stand-alone evaluations, an added value. Very little has been done to integrate environmental impacts as a part of pavement management systems and other decision support tools to choose between different strategies. In this way, being awarded with a "green" certificate for a specific road project could result in the belief that recognition would correspond to the optimal strategy. Furthermore, a road project awarded with a "green" rating during the construction phase does not mean that the project results "green" if a life cycle approach is considered. Indeed, the most environmental friendly strategies may not be the ones with the highest performance. Using "greener" materials or performing recycle-related practices may lead to a lower performance over the life cycle and therefore produce an increase in maintenance needed, which could in turn result into more congestion due to work zones and higher total emissions. Therefore, construction and maintenance strategies should be analyzed according to three main parameters: cost, performance or effectiveness, and environmental impacts. The cost analysis part takes into account outflows over the service life of the pavement according to the well-known Life Cycle Cost Analysis methodology. The cheapest maintenance technique over the analysis period was expounded and sensitivity analyses to involved factors were conducted. Performance assessment was developed according to experimental on site data gathered and analyzed over several years to develop deterioration pavement models. Effectiveness of maintenance treatments is further provided and compared to the volume of traffic. In addition, environmental impacts related to maintenance and rehabilitation strategies were analyzed. Emissions were computed over the life cycle of the pavement from the manufacture of raw materials for the initial construction, placement, and maintenance phase. Finally, an optimization procedure was developed for including environmental impacts into a Pavement Management System. A methodology to set a multi-attribute approach system, computing costs, performance, and eco-efficiency over the life cycle of the pavement, is therefore proposed.

In recent decades pavement management optimization has been designed with the objective of minimizing user and agency life-cycle costs. However, pavement management decisions also have significant impacts on life-cycle energy use and environmental emissions from pavement management activity and user vehicles. This study expands beyond optimizing pavement rehabilitation strategy for minimization of life-cycle costs to also include greenhouse gas (GHG) emissions. We extend previous work on the single-facility, continuous-state, continuous-time optimal pavement resurfacing problem to solve the multi-criteria optimization problem with the two objectives of minimizing costs and GHG emissions. The balance between the potentially two different optimal rehabilitation policies is found through the use of a Pareto frontier, which exists in the span between the cost- and emission- optimal strategies. The Pareto frontier provides decision makers with the dollars per tonne of GHG emissions saved due to a change in rehabilitation strategy. Results using California data indicate that there is a tradeoff between costs and emissions when developing a pavement resurfacing strategy, providing a range of GHG emissions reduction cost-effectiveness options. Case studies for a two-lane arterial and a ten-lane major highway in California are presented, where traditional hot-mix asphalt overlays are applied. The 2011 case studies are particular to California by traffic loadings and pavement durability. However, the user and agency emission and cost estimations are based on national data. Thus, generalizing the case study results should be subject to these caveats. An ordinary medium-volume metropolitan state-designed road and an extremely heavily traveled highway bearing commuters into and from San Francisco are optimized as representative situations. Results for a one-kilometer segment of Interstate 80, in Berkeley California, with ten lanes and 273,000 light-duty vehicles and 13,100 heavy-duty vehicles per day, indicate that the life-cycle cost minimum occurs when asphalt overlays are applied every 15 years or equivalently when the pavement roughness reaches an international roughness index (IRI) of 2.7 m/km. Coincidentally, this is the same roughness Caltrans uses to decide when to apply an overlay for the state's roads. However, where any of the conditions or characteristics for any pavement segments are different, the coincidence may cease to exist. The minimum life-cycle cost at this optimal pavement rehabilitation strategy is approximately $490,000 per kilometer per year, at which point resurfacing activity and user vehicles would emit approximately 220 tonnes of CO2 equivalents per kilometer per year. The GHG emissions minimum corresponds to an overlay interval of 22 years or the equivalent threshold roughness IRI of 3.4 m/km. The minimum GHG emissions (user emissions plus agency emissions) are approximately 200 tonnes of CO2 equivalents per kilometer per year, with life-cycle costs (user costs plus agency costs) at approximately $520,000 per kilometer per year. Agency and user emission (and cost) estimates each change in opposing directions when overlay intervals change. Thus, when each of the like agency and user attributes are added together, a minimum is guaranteed to exist. Any pavement rehabilitation strategy that makes use of overlay intervals outside of this sub-interval defined by the life-cycle cost and GHG emissions optima are trivial in that any strategy change designed to reduce costs also reduces emissions. However, inside this special sub-interval, any change in strategy that reduces costs will increase emissions and vice versa. Thus, this special sub-interval constitutes a Pareto frontier of optimal solutions where tradeoffs are associated with each change. For example, if Caltrans is currently operating at the life-cycle cost minimum by applying an overlay interval every 15 years but decides to reduce emissions by changing the interval to every 18 years, there will be a reduction in emissions. However, it will come at a total life-cycle cost of approximately $500 per tonne of CO2 equivalents. Of course different pavement rehabilitation strategy changes will present different cost-effectiveness ratios. If the change spans points outside the Pareto frontier, the costs may be minimal or even negative. However, within the Pareto frontier, attempts to save even more emissions will increase costs per unit of CO2 equivalents saved.If a market value for CO2 exists, then a unique optimal pavement rehabilitation strategy is defined. On the Pareto frontier is every possible market value as the negative of the slope of the tangent line to each point on the curve represents a market value starting with zero dollars per tonne of emissions (cost minimum) to infinite dollars per tonne of emissions (emissions minimum).Results for a two-lane arterial road segment, also in Berkeley, which has only 25,000 light-duty vehicles and 480 heavy-duty vehicles per day, indicate that similar pavement rehabilitation strategy overlay intervals are optimal. For the life-cycle cost minimum, a 16-year overlay interval is optimal, which corresponds to a threshold roughness IRI of 2.1 m/km. For the GHG emissions minimum, an overlay interval of 25 years and its associated threshold roughness IRI of 2.5 m/km are optimal. Although the overlay intervals are not that different from the larger ten-lane interstate highway case, the threshold roughness values are more favorable in the two-lane case. The life-cycle cost minimum occurs at approximately $80,000 per kilometer per year and is associated with approximately 51 tonnes of CO2 equivalents per kilometer per year. The GHG emissions minimum occurs at approximately 47 tonnes of CO2 equivalents per kilometer per year and is associated with approximately $86,000 per kilometer per year. A sensitivity analysis on model input parameters revealed which parameters required the best accuracy and shed light on policy decisions. Pavement deterioration rate, within a 20% variation, had a relatively little effect on outcomes. This indicates that uncertainty around the pavement deterioration rate is not very important. However, a small change in vehicle miles traveled had a large effect on outcomes. Other results highlighted the contrast between strategy decisions for various pavement and vehicle technologies. For example, it is found that, in both case studies, improving vehicle fleet fuel economy will save total (tailpipe plus pavement) emissions. The two-lane case showed a larger percentage of relative reduction in emissions but the ten-lane case was found to have a larger total reduction in emissions. However, an improved fuel economy for the vehicle fleets means that the effect of roughness on fuel consumption is less. Thus, the GHG emissions associated with pavement management become a larger share of the total emissions. This means that at the emissions optimal, the pavements are allowed to become rougher before being rehabilitated again. Thus, to counteract the expected fuel economy improvements of the future, the use of new technologies that reduce emissions associated with pavement overlay activity, but also reduce roughness at optimality, is paramount. For the same reason, technologies that provide more durable pavements are also encouraged.

The performance of different pavement maintenance treatments were evaluated by investigating practical projects collected from Tennessee Pavement Management System (PMS) and Long Term Pavement Performance (LTPP) database. The influence of factors on the effectiveness, cost-effectiveness and cracking initiation of different treatment were evaluated by “Optime”, multiple linear regression and parametric survival analysis. Pavement roughness, pavement serviceability index (PSI) and the initiation time of cracking were used as pavement performance indicators. Investigation on the pavement maintenance projects in Tennessee by Optime and multiple linear regression analysis indicated that HMA overlay had the highest effectiveness, followed by mill & fill and micro surfacing. Due to the relatively low cost, micro surfacing was the most cost-effective treatment, followed by HMA overlay and mill & fill. The effectiveness and cost-effectiveness decreased with the increase of traffic level and pre-treatment pavement condition. Investigation on the LTPP resurfacing treatments indicated that thick overlay and milling reduced the roughness after rehabilitation. Thin overlay, high traffic level and poor pre-rehabilitation pavement condition increased the deterioration rate of new overlay. Using reclaimed asphalt material did not influence the treatment performance but was cost-effective in reducing the roughness of new overlay. For a certain deterioration rate, there was an optimized pre-rehabilitation roughness value or time for applying maintenance treatment. Survival analysis on the crack initiation of asphalt overlay indicated that high traffic level accelerated the initiation of cracking. Thick overlay delayed the initiation of cracking except for the non-wheel path longitudinal crack. Mill retarded the occurrence of the non-fatigue cracks, whereas severe freeze thaw condition accelerated the occurrence of the two types of cracking. Using 30% RAP accelerated the initiation of longitudinal fatigue crack on wheel path but did not cause serious fatigue problem. The performance curves of HMA resurfacing treatments used in Tennessee were calibrated by investigating the influence of different factors on the slopes and intercepts of post-treatment performance curves. The analysis indicated that pavement with high pre-treatment PSI, thick overlay and deep milling had low deterioration rate, whereas pavement with higher traffic level deteriorated faster.