Acknowledgements

The research presented in this paper was supported by finding from the Mountain-Plains Consortium (U.S. Department of Transportation) and the Utah Department of Transportation through the Utah Transportation Center.

Disclaimer

The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented. This document is disseminated under the sponsorship of the Department of Transportation, University Transportation Centers Program, in the interest of information exchange. The U.S. Government assumes no liability for the contents or use thereof.

List of Acronyms

Executive Summary

In May of 2001, 16 miles of high-occupancy vehicle (HOV) lane opened on the re-constructed Interstate 15 (I-15). The HOV lanes operate between 600 North and 10600 South in the Salt Lake Valley. A single northbound HOV lane and a single southbound HOV lane are separated from the four general-purpose freeway lanes in both directions by striping that allows HOV lane entrance and exit. The HOV lanes operate twenty-four hours a day and allow vehicles with two or more occupants, motorcycles, and transit vehicles. The only HOV-specific access to an arterial is located at 400 South and allows HOV-only direct access to the I-15 southbound on-ramp and the I-15 northbound off-ramp. This paper reports on a two-year study evaluating HOV lane performance. The analysis assesses the freeway operations before the HOV lanes opened with continued assessment throughout the first year of operation. It looks at automatic data from traffic monitoring stations and manual data from roadside and travel time surveys.

The findings indicate that during the afternoon peak period, the HOV lane moves the same number of people as each general-purpose (GP) lane with only 44 percent of the vehicles. However, the HOV lane moves fewer people than its GP lane counterparts throughout the rest of the day during times of little or no congestion. HOV lanes show travel time savings for HOV users. According to measures of travel time between 400 South and 10600 South, relative to the adjacent GP lanes, the HOV lanes provide a 30 percent travel time savings during the afternoon peak period and a 13 percent travel time savings during the morning peak time. Furthermore, unlike the higher variation of travel times on GP lanes, HOV lanes provide a more consistent and predictable travel time because of lower rates of congestion and incidents. The HOV lanes' violation rates range from 5 percent to 13 percent along the I-15 corridor, which is slightly higher than the 5 to 10 percent expected by national averages. At the 400 South HOV on /off ramp the violation rates increase to 20 percent. Recurring surveys during the initial year of HOV operations show that violation rates initially reduced after the HOV lane opening and have since stabilized. Average vehicle occupancy on I-215 and non-HOV portions of I-15 have remained the same before and since the HOV lane opening. Vehicle occupancy on the I-15 corridors with HOV lanes experienced a 17 percent increase, from 1.1 persons per vehicle to 1.3. Therefore, public support of HOV lanes has resulted in carpooling. Though HOV lanes are successful and anticipated to be increasingly valuable as the congestion in the Salt Lake Valley increases, this report offers recommendations to improve the HOV lanes' performance.