Using Project Level Drive Cycles to Support Air Quality Analysis
Research Idea Scope
The objective of this project is to develop guidance on how to apply microscopic traffic simulation models to project level emissions analysis, focusing specifically on vehicle trajectory information. This project would take advantage of already completed research and to bundle it into step-by-step guidance for practitioners at up to two levels of analysis: (1) sketch planning and (2) preliminary engineering. At the sketch planning level, a compendium of typical drive cycles was develop by FHWA several years ago by applying microscopic simulation to a series of experiments. Drive cycles were developed for several factors: v/c ratio, relation of highway section to a bottleneck or traffic signal, ramp configuration (on-ramp versus freeway-to-freeway), and incident conditions. The drive cycles were developed for cases where only a limited amount of data are available, such as output from travel demand forecasting models. However, no guidance has been developed on how to apply the drive cycle information within a sketch planning environment. This project would develop the procedures and show examples of how the drive cycles can be applied to projects at the sketch planning level such as when a range of potential improvements are screened. Detailed requirements will be developed as well as an analytical engine (i.e., analysis software) for testing the guidance. Illustrative emissions impacts will also be shown to help practitioners understand how both criteria pollutant and GHG emissions might vary under a range of project alternatives for different types of projects. Optionally, the study could be expanded to include guidance for the For Preliminary Engineering level. Increasingly, this stage of project development includes microsimulation analysis of a few project alternatives. The guidance here will involve writing the technical requirements for a microsimulation model post-processor that takes the detailed vehicle trajectories output from these models and translates them into emissions estimates based on the MOVES drive cycles. The project will take advantage of any recent research that has compared microsimulation trajectories to empirically measured trajectories for the purpose of developing adjustment factors to the model-derived trajectories. The requirements will be developed so that agencies can develop their own software to do the post-processing. An analytical engine (i.e., analysis software) will be developed by the team for the purpose of testing.
Urgency and Payoff
This project would provide practitioners with tools to develop better estimates of emissions for project-level air quality and/or GHG analysis. In most cases, project-level assessments are based on average speeds. Information from typical drive cycles has been developed but is not readily accessible; this project would make it easier for practitioners to apply this information. The presentation of illustrative impacts would help practitioners understand when it is worthwhile (or not) to model emissions impacts based on vehicle trajectories rather than average speeds. This will also support ongoing NCHRP work under Project 25-56 to develop a guidebook for how state DOTs can reduce GHG emissions – the existing tools for project level evaluation are limited. In addition to making use of typical drive cycles, the optional 2nd phase of this project would assist practitioners in applying microsimulation models for project level air quality analysis by adjusting for known differences between modeled and real-world drive cycles.
Chris Porter Cambridge Systematics, Inc. 781-539-6723