1. Introduction
High Occupancy Vehicle (HOV) lanes exist throughout North America to maximize the person-carrying capacity of a facility by offering travel time savings as well as reliable and predictable travel times. HOV lanes in several states, including New Jersey, California, and Virginia, have recently received criticism for what is termed the "empty lane syndrome," or perceived underutilization of HOV lanes. Two facilities in New Jersey, I-80 and I-287, were decommissioned in November 1998 due to political pressure. In these particular cases the facilities lacked some of the fundamental design and operational characteristics common to successful HOV lanes and local users deemed the lanes wasteful (1,2,3).
In May of 2001, UDOT completed its I-15 reconstruction in Salt Lake City, incorporating sixteen miles of HOV lanes. The reconstruction increased I-15 from three General Purpose (GP) lanes in each direction to four GP lanes and one HOV lane in both directions. This report documents a two-year research study regarding the operation and usage of I-15 one year prior to the HOV lane opening and during the first year of HOV operations. Volume, speeds, vehicle occupancy, and violation rates for HOV and GP lanes are compared to one another. In addition, these variables are compared between pre-HOV I-15 and reconstructed HOV I-15.
Figure 1.1 shows the I-15 HOV lanes located from 600 North to 10600 South in the Salt Lake Valley. A solid white stripe separates the single HOV lane from the four northbound and southbound GP lanes. The open-access stripe allows maximum flexibility for users, however it also provides easy access for Single Occupancy Vehicles (SOVs) to misuse the HOV lane for queue jumping. Exclusive HOV on-ramps are located at 400 South, near the CBD of Salt Lake City. In regard to the current operating policies, the HOV lanes are enforced 24 hours a day, seven days a week and reserve usage to vehicles with two or more passengers (carpools, vanpools and buses) and motorcycles. The question of continuous enforcement or operation during peak hours is being assessed nationwide.
Figure 1.1 HOV Lanes along 1-15 Corridor in Salt Lake Valley
Transportation is the movement of people or goods from where they are to where they are of more value or want to be. Therefore, moving vehicles is not an inherent goal of transportation. However, if more people can be moved in fewer vehicles, congestion is reduced and the transportation system is more efficient. One of the main objectives of the I-15 HOV lanes, and HOV lanes in general, is to increase the average number of persons per vehicle. Knowing the effectiveness of the I-15 HOV lanes is important for policy-making decisions, including whether to implement HOV lanes on other freeways in the area and whether the minimum passenger level should be raised. HOV lane violation rates indicate the degree of public acceptance of HOV lanes and also measure the risks versus the benefits of violation. While this report documents the assessment of the first year of HOV operation, ongoing assessment and monitoring is the key to continued acceptance and successful operation of HOV lanes. This continuous monitoring allows decisions to be made about HOV operations and benefits as freeway congestion increases. The success and benefit of HOV lanes should continue to increase as congestion in the Salt Lake Valley increases.
The Utah Department of Transportation (UDOT), in conjunction with the University of Utah and Mountain Plains Consortium, a federally supported ITS program, conducted a two-year study. The project sought to measure HOV lane effectiveness. The study's research objectives are:
- Evaluate the impact of HOV lanes on I-15 and alternate routes.
- Measure the effectiveness of HOV lanes by comparing before-HOV-lane statistics with after-HOV-lane statistics.
- Recommend changes to existing HOV operations policies or procedures.
- Review and recommend educational programs for improving HOV lane acceptance and compliance.
It is important to assess the HOV lane's performance because the recent increase in capacity of I-15 may actually promote a decrease in occupancy by increasing available travel opportunities. To meet the research objectives mentioned above and determine whether the HOV lane is successful, the following tasks were completed:
- Review of success and failures in other metropolitan areas
- Determine measure of effectiveness (MOEs)
- Collect field data with and without the HOV lanes operating
- Evaluate effectiveness and acceptance
- Measure the benefits provided by HOV lanes