Traffic Assignment and Operating Mode Modeling

In this research, we are developing a joint traffic assignment and operating mode modeling procedure in which the elapsed time of trips will be traced and recorded as they are assigned on each link along their path of travel within the assignment. Thus, at the end of this step, the volumes on each link are classified into transient and stabilized modes on the basis of whether the elapsed time from the origin exceeds 505 seconds or not. Models are being developed for each purpose by time of day to further split the transient mode into cold starts or hot starts using the 1996 activity diary data collected by the Dallas-Fort Worth MPO. The proposed procedure will provide better estimates of operating mode fractions since it is based on trip-ends by purpose and time-of-day as estimated using local data. Further, the proposed approach is able to represent operating mode fraction changes by link and time-of-day in response to TCMs. This is important since the emission factor models are very sensitive to the operating mode distribution and using methods that use an operating mode distribution which does not vary across links might provide inappropriate emission results.