Applying Dynamic Modeling Methods to IH 35 Through Austin: Exploring Options for Addressing Future Congestion

Abstract

The City of Austin is among the fastest-growing cities in the U.S., with the surrounding counties keeping a similar pace. Travel times from downtown Austin to Round Rock, where many commuters live, currently range from 45 to 60 minutes during the average afternoon rush hour. Decision-makers have expressed a need to examine long-term solutions for IH 35 to explore concepts discussed under previous studies. This study applied dynamic traffic assignment coupled with static and dynamic tolling analysis, user class restrictions and multi-class simulation and assignment to examine various long-term scenarios with potential to address growing congestion on this critical corridor. The findings were illuminating: if residential and employment growth continue on their current pace through 2035, the region wide dynamic traffic assignment results applied at the mesoscopic level in this study demonstrate that Central Texas faces a grim future of extreme traffic congestion on IH 35. While an added capacity scenario was identified which can address future IH 35 congestion in some instances, it is of questionable viability for implementation. The scenario with the largest capacity addition did not provide the best results due to limited accessibility and only when the limits were extended dramatically, did researchers find more positive congestion relief. However, this scenario would be the highest investment and would probably be deemed infeasible simply due to cost. A more positive finding was that a hybrid strategy of added capacity, dynamic tolling, and travel demand management solutions demonstrates even greater benefits. When all options were considered, it was realized that added capacity would not be enough; it would need to be coupled with managed lanes, changes in travel behavior, more efficient land use, demand management and increased transit use.