The purpose of this research was to quantify health co-benefits and carbon reductions of preferred scenarios of California regional transportation plans and alternatives with ambitious levels of active transport. The alternatives were designed to examine the efficacy of independent contributions of walking, bicycling, and transit at levels consistent with the U.S. Surgeon General recommendation for physical activity. Using data from travel and health surveys, vital statistics, collision databases, and outputs from regional and statewide travel models, the Integrated Transport and Health Impacts Model estimated the change in the population disease burden, as measured by deaths and disability adjusted life years (DALYs), due to a shift from a 2010 baseline travel pattern to an alternative. Health pathways modeled were physical activity and road traffic injuries. The preferred scenarios increased statewide active transport from 40.5 to 53.4 min person−1 w−1, which was associated with an annual decrease of 909 deaths and 16,089 DALYs. Sensitivity analyses that accounted for 2040 projected age- and sex-specific population characteristics and cause-specific mortality rates did not appreciably alter the annual change in deaths and DALYs on a population basis. The ambitious, maximal alternatives increased population mean travel duration to 283 min person−1 w−1 for walking, bicycling, or transit and were associated a reduction in deaths and DALYs from 2.5 to 12 times greater than the California preferred scenarios. The alternative with the largest health impact was bicycling 283 min person−1 w−1 which led to 8,543 fewer annual deaths and 194,003 fewer DALYs, despite an increase in bicyclist injuries. With anticipated population growth, no alternative achieved decreases in carbon emissions but bicycling had the greatest potential for slowing their growth. Alternatives that included transit similarly reduced carbon emissions, but with less health benefit. Aggressive expansion of active transport is an efficacious, but underutilized policy option with significant health co-benefits for mitigating greenhouse gases.

The Biham-Middleton-Levine model (BML) is simple lattice model of traffic flow, self-organization and jamming. Rather than a sharp phase transition between free-flow and jammed, it was recently shown that there is a region where stable intermediate states exist, with details dependent on the aspect ratio of the underlying lattice. Here we investigate square aspect ratios, focusing on the region where random, disordered intermediate (DI) states and conventional global jam (GJ) states coexist, and show that DI states dominate for some densities and timescales. Moreover, we show that periodic intermediate (PI) states can also coexist. PI states converge to periodic limit cycles with short recurrence times and were previously conjectured to arise from idiosyncrasies of relatively prime aspect ratios. The observed coexistence of DI, PI and GJ states shows that global parameters, density together with aspect ratio, are not sufficient to determine the full jamming outcome. We investigate additional features that lead towards jamming and show that a strategic perturbation of a few selected bits can change the nature of the flow, nucleating a global jam.

This study investigated the potential changes in transportation patterns in California associated with the development of smart growth–inspired transportation and land use policies through the application of the California Statewide Travel Demand Model (CSTDM). California's SB (Senate Bill) 375 requires the state's metropolitan planning organizations (MPOs) to develop sustainable community strategies (SCS) in their regional transportation plans (RTPs) in an effort to reduce greenhouse gas emissions, among other environmental goals, through the integration of land use and transportation planning. Although some SCS were still under development at the time this study was conducted, some concerns had already been raised about whether these proposed policies would be able to achieve the proposed environmental targets. In this study, future transportation demand in California in 2035 was simulated through the application of the CSTDM and the simulation of policy scenarios inspired by the SCS developed before February 2014 by local MPOs. The study provides insights into how proposed land use changes and planned transportation investments would affect both regional and interregional mobility patterns in California. The expected impacts of the proposed policies were compared with a more conservative control scenario based on the previous RTPs developed by MPOs before the introduction of the SCS. Reductions of vehicle miles traveled per capita were predicted for all regions that had developed SCS, with greater reductions in larger metropolitan areas.

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