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I-25 HOV/Tolled Express Lane Project


I-25 HOV-Tolled Express Lanes

WSP USA was involved in every aspect—from conceptualization to operation—of adapting the I-25 high-occupancy vehicle (HOV) lanes to approximately 7 miles of HOV/tolled express lanes. 

After our feasibility studies and public outreach program determined that motorists would accept tolled express lanes, we evaluated future traffic operations and tolling requirements for converting the HOV lanes to tolled express lanes. Using CORSIM and VISSIM models, we simulated express-lane operations under various design alternatives and determined how forecasted traffic would affect transit riders, HOV users, and downtown residents. Other tasks included evaluating the impact of express-lane operations on regional air-quality conformity; estimating traffic and revenue forecasts using variable-pricing schemes; assisting in the development of the initial variable-toll schedule to estimate traffic use; and establishing a performance evaluation process to refine the toll rate over time. We also prepared preliminary and final plans, specifications and estimates for signing, striping, paving, barrier relocation, and installation of electrical and fiber-optic lines to aid in toll collection. 

Throughout the project, we assisted the Colorado Department of Transportation (CDOT) and its High-Performance Transportation Enterprise (HPTE) with public outreach/information, including the production of an educational video. 

Accommodating transit interests was a key component of the project. We helped create an intergovernmental agreement (IGA) between CDOT and the Regional Transportation District (RTD) which operates public transit services in eight of the 12 counties in the Denver-Aurora-Boulder area. Under the IGA, the peak-hour toll rates were set to the equivalent of the prevailing express-bus fare, which provided an incentive for commuters to use transit. In addition, express-lane performance and future toll-rate adjustments were benchmarked to bus travel times in the express lanes, which provided an automated database for examining performance. 

Under a separate contract, we served as technical advisor to the CDOT for a peer review of other HOV projects in the nation that were converted to express lanes prior to the release of Federal Highway Administration (FHWA) guidelines. The purpose of the peer review was to demonstrate to CDOT and the FHWA that the outreach program for the I-25 express lanes was consistent with the outreach efforts studied in the peer review and would provide a comprehensive understanding of the public’s opinion regarding tolling.