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Public transit systems with high occupancy can reduce greenhouse gas (GHG) emissions relative to low-occupancy transportation modes, but current transit systems have not been designed to reduce environmental impacts. This motivates the study of the benefits of design and operational approaches for reducing the environmental impacts of transit systems. For example, transit agencies may replace level-of-service (LOS) by vehicle miles traveled (VMT) as a criterion in evaluating design and operational changes. In previous work, we explored the unintended consequences of lowering transit LOS on emissions in a single-technology transit system. Herein, we extend the analysis to account for a more realistic case: a transit system with a hierarchical structure (trunk and feeder lines) providing service to a city where demand is elastic. By considering the interactions between the trunk and the feeder systems, we provide a quantitative basis for designing and operating integrated urban transit systems that can reduce GHG emissions and societal costs. We find that highly elastic transit demand may cancel emission reduction potentials resulting from lowering LOS, due to demand shifts to lower occupancy vehicles. However, for mass transit modes, these potentials are still significant. Transit networks with buses, bus rapid transit or light rail as trunk modes should be designed and operated near the cost-optimal point when the demand is highly elastic, while this is not required for metro. We find that the potential for unintended consequences increases with the size of the city. Our results are robust to uncertainties in the costs and emissions parameters. [ABSTRACT FROM AUTHOR]

Abstract: This article uses life-cycle assessment to evaluate the role of long-life pavements in achieving environmental goals. The success of such pavements in reducing environmental impacts over their life cycle hinges on their ability to serve their intended purpose for their design life. Those pavements that do serve for their entire design life offer extreme longevity at only a marginal environmental cost. However, the return on the initial environmental investment occurs after many decades of use and is often beyond conventional analysis periods. Evolving performance expectations and demand create uncertainty regarding the ability of long-life pavements to reach environmental goals because time-dependent factors, such as technology shifts and functional obsolescence, affect their ability to serve for their entire design life. [ABSTRACT FROM AUTHOR]