California Partners for Advanced Transportation Technology

This report documents our validation effort on the Incremental Transfer (IT) model, which is a macroscopic traffic flow model capable of handling freeway systems with special lanes and priority vehicles. The validation study is performed with field data from a 1.7-mile long freeway segment with a congested off-ramp in Oakland, California. In our study, vehicles exiting the off- ramp of this segment are treated as "regular vehicles" and through vehicles as "special vehicles." By assuming that the exiting or "regular" vehicles must stay on the "near" side lanes, we examine the spatial evolution of separate versus coalesced queues developed in the region resulting from a capacity reduction on the exit ramp. The observed queuing pattern is then compared with that predicted by the IT model. Qualitatively, the IT model yields a queuing pattern similar to the one observed in the field data. The model predicts the separate versus coalesced queues in a way that no other macroscopic traffic flow models can do. However, the predictions of the exact queue location are not accurate. The errors may be caused by the lack of sufficient input information required by the model and the difference between the unique traffic characteristics of the test site and model assumptions.