As road conditions worsen, users experience an increase in fuel consumption and vehicle wear and tear. This increases the costs incurred by the drivers, and also increases the amount of greenhouse gases (GHGs) that vehicles emit. Pavement condition can be improved through rehabilitation activities (resurfacing) to reduce the effects on users, but these activities also have significant cost and GHG emission impacts. The objective of pavement management is to minimize total societal (user and agency) costs. However, the environmental impacts associated with the cost-minimizing policy are not currently accounted for. We show that there exists a range of potentially optimal decisions, known as the Pareto frontier, in which it is not possible to decrease total emissions without increasing total costs and vice versa. This research explores these tradeoffs for a system of pavement segments. For a case study, a network was created from a subset of California's highways using available traffic data. It was shown that the current resurfacing strategy used by the state's transportation agency, Caltrans, does not fall on the Pareto frontier, meaning that significant savings in both total costs and total emissions can be achieved by switching to one of the optimal policies. The methods presented in this paper also allow the decision maker to evaluate the impact of other policies, such as reduced vehicle kilometers traveled or better construction standards.
Pavement management systems, designed to minimize total lifecycle costs, will need to evolve to meet the needs of the future. Environmental concerns are likely to add an additional consideration for the state DOTs when allocating their financial resources. Transportation agencies will be concerned with determining maintenance, resurfacing and reconstruction policies for pavement segments in their systems while also addressing the environmental impact of these activities. In this paper, we propose an efficient solution to solve for pavement resurfacing and reconstruction policies that minimize societal (agency and user) costs under a Greenhouse Gas (GHG) emissions constraint. The main methodological contribution of this work relative to the state of the art is that we formulate the problem to include multi-dimensional pavement segment states and heterogeneous management activities. It allows for a more realistic representation of the majority of current pavements in the world. For example, the assumption that pavements are perpetual, i.e., do not need reconstruction during their lifetime, can be relaxed. A case study using California roads is performed; we find that, for that specific group of pavement segments, the optimal policies to minimize societal costs do not vary greatly from the policies that minimize GHG emissions. An agency can use these results to determine what GHG emission budgets are feasible for the highway system that it manages.
Transportation agencies are being urged to reduce their greenhouse gas (GHG) emissions. One possible solution within their scope is to alter their pavement management system to include environmental impacts. Managing pavement assets is important because poor road conditions lead to increased fuel consumption of vehicles. Rehabilitation activities improve pavement condition, but require materials and construction equipment, which produce GHG emissions as well. The agency's role is to decide when to rehabilitate the road segments in the network. In previous work, we sought to minimize total societal costs (user and agency costs combined) subject to an emissions constraint for a road network, and demonstrated that there exists a range of potentially optimal solutions (a Pareto frontier) with tradeoffs between costs and GHG emissions. However, we did not account for the case where the available financial budget to the agency is binding. This letter considers an agency whose main goal is to reduce its carbon footprint while operating under a constrained financial budget. A Lagrangian dual solution methodology is applied, which selects the optimal timing and optimal action from a set of alternatives for each segment. This formulation quantifies GHG emission savings per additional dollar of agency budget spent, which can be used in a cap-and-trade system or to make budget decisions. We discuss the importance of communication between agencies and their legislature that sets the financial budgets to implement sustainable policies. We show that for a case study of Californian roads, it is optimal to apply frequent, thin overlays as opposed to the less frequent, thick overlays recommended in the literature if the objective is to minimize GHG emissions. A promising new technology, warm-mix asphalt, will have a negligible effect on reducing GHG emissions for road resurfacing under constrained budgets.
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