Modeling Soak-Time Distribution of Trips for Mobile Source Emissions Forecasting: Techniques and Applications

The soak time of vehicle trip starts is defined as the duration of time in which the vehicle’s engine is not operating and that precedes a successful vehicle start. The temporal distribution of the soak time in an area is an important determinant of areawide mobile source emissions. In this study, a methodology for modeling soak-time durations is formulated and implemented. The methodology involves estimation of models using vehicle trip data from household travel surveys and supplementary zonal demographic and land use data. The effectiveness of the methodology lies in its easy application at the traffic zonal level within a metropolitan region to obtain zone-specific soak-time distributions by time of day and origin activity purpose. The methodology is applied to estimate soak-time duration models for the Dallas–Fort Worth area of Texas.