Safety Evaluation of HOV Lane Design Elements

Project Description

This project performed an in-depth safety evaluation of high-occupancy vehicle (HOV) lanes in Dallas. The safety evaluation focused on two buffer-separated concurrent flow HOV lanes (IH-35E and IH-635), which were implemented by reducing lane widths and converting the inside shoulder into the HOV lane on both corridors. The IH-30 East R.L. Thornton barrier-separated HOV lane was also evaluated. Injury crash data from each corridor were analyzed based on crash rates, frequency trends, and manually reviewing police reports. The analysis considered the impact of design elements including buffer width, shoulder presence, and lane width. Operationally, the analysis considered the impact of speed differential between the HOV and general-purpose lanes. This evaluation resulted in three key findings:

• Both corridors had an increase in crash rates after implementation of the HOV lane.
• The increase in crashes is primarily focused on the HOV lane and the first adjacent general-purpose lane.
• The increase in crashes is primarily attributed to the speed differential between the HOV and the general-purposes lanes and the reduced HOV cross section.

The recommendation, based on these findings, is to provide greater width for the total HOV cross section (inside shoulder + HOV lane + painted-buffer) than that provided in the two interim corridors. An absolute minimum of eighteen feet between the freeway barrier and the general-purpose lanes may mitigate many of the types of crashes that occur due to the speed differential, with full inside shoulders being the desirable cross section.

Project Publications

Crash Analysis of Selected High-Occupancy Vehicle Facilities in Texas: Methodology, Findings, and Recommendations 0-4434-1

Guidance for Future Design of Freeways with High-Occupancy Vehicle (HOV) Lanes Based on an Analysis of Crash Data from Dallas, Texas 0-4434-P1

Crash Data Identify Safety Issues for High-Occupancy Vehicle Lanes in Selected Texas Corridors 0-4434-S

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