Active Travel Co-Benefits of Travel Demand Management Policies that Reduce Greenhouse Gas Emissions, MTI Report 12-12

There is increasing evidence that improved health outcomes may be significant co-benefits of land use plans and transport policies that increase active transport (or walking and biking for purposeful travel) and reduce greenhouse gas emissions (GHGs) from vehicle miles traveled (VMT). A greater understanding of these benefits may broaden the constituency for regional planning that supports local and national GHG reduction goals. In this study, California’s activity-based travel demand model (ABM) is applied to (1) demonstrate how this new generation of travel models can be used to produce the active travel data (age and sex distributions) required by comparative risk assessment models to estimate health outcomes for alternative land use and transport plans and to (2) identify the magnitude of change in active travel that may be possible from land use, transit, and vehicle pricing policies for California and its five major regions for a future 2035 time horizon. The results of this study suggest that distance-based vehicle pricing may increase walking by about 10% and biking by about 17%, and concurrently GHG from VMT may be reduced by about 16%. Transit expansion and supportive development patterns may increase active travel by about 2% to 3% for both walk and bike modes while also reducing VMT by about 4% on average. The combination of all three policies may increase time spent walking by about 13% and biking by about 19%, and reduce VMT by about 19%

Periodic States, Local Effects and Coexistence in the BML Traffic Jam Model

The Biham-Middleton-Levine model (BML) is simple lattice model of traffic flow, self-organization and jamming. Recently, the conventional understanding was shown to be incomplete: rather than a sharp phase transition between free-flow and jammed, there is an additional region where convergence to intermediate states is observed, with details dependent on the aspect ratio of the underlying lattice. For aspect ratios formed by two subsequent Fibonacci numbers, intermediate states converge to ordered, periodic limit cycles (i.e., periodic intermediate (PI) states). In contrast, for square aspect ratios, intermediate states typically converge to random, disordered intermediate (DI) states. We show these DI states are very robust to perturbation and occur more frequently than the conventional states for some densities. Furthermore, we report here on the discovery of PI states on square aspect ratios, showing PI states are not just an idiosyncrasy of particular aspect ratios. Finally, we investigate features that lead towards jamming and identify that local effects can dominate. A strategic perturbation of a few selected bits can change the nature of the flow, nucleating a global jam. The global parameters, density together with aspect ratio, are not sufficient to determine the full jamming outcome

Periodic States, Local Effects and Coexistence in the BML Traffic Jam Model

The Biham-Middleton-Levine model (BML) is simple lattice model of traffic flow, self-organization and jamming. Recently, the conventional understanding was shown to be incomplete: rather than a sharp phase transition between free-flow and jammed, there is an additional region where convergence to intermediate states is observed, with details dependent on the aspect ratio of the underlying lattice. For aspect ratios formed by two subsequent Fibonacci numbers, intermediate states converge to ordered, periodic limit cycles (i.e., periodic intermediate (PI) states). In contrast, for square aspect ratios, intermediate states typically converge to random, disordered intermediate (DI) states. We show these DI states are very robust to perturbation and occur more frequently than the conventional states for some densities. Furthermore, we report here on the discovery of PI states on square aspect ratios, showing PI states are not just an idiosyncrasy of particular aspect ratios. Finally, we investigate features that lead towards jamming and identify that local effects can dominate. A strategic perturbation of a few selected bits can change the nature of the flow, nucleating a global jam. The global parameters, density together with aspect ratio, are not sufficient to determine the full jamming outcome.UCD-ITS-RR-07-24, Civil Engineering