Traffic Control Device Evaluation Program: Technical Report

Author/Presenter: Carlson, Paul J.; Higgins, Laura L.; Pratt, Michael P.; Finley, Melisa D.; Theiss, LuAnn; Williams, William F.; Iragavarapu, Vichika; Ko, Myunghoon; Nelson, Alicia A.
Abstract:

This project provides the Texas Department of Transportation with a mechanism to quickly and effectively conduct high-priority, limited scope evaluations of traffic control devices. Work during the 2013—2014 fiscal year included three main tasks: updating the Texas Curve Advisory Speed (TCAS) program, testing alternatives to the existing exit gore sign requirements, and evaluating pilot vehicles and portable traffic control signals with and without a flagger.

The TCAS program was developed to assist practitioners in the implementation of the guidelines for setting curve advisory speeds and choosing curve traffic control devices. Researchers updated the calculations contained within the TCAS program to reflect the guidelines in the Texas Manual on Traffic Control Devices (TMUTCD). Researchers also added a new set of calculations so that users have the choice of applying either the TMUTCD or the Procedures for Establishing Speed Zones.

Exit gore signs are often hit and require constant maintenance, which puts maintenance crews at risk. The study’s objective was to develop potential alternative(s) to provide the road user the same level of information but reduce or eliminate the risk during maintenance. Researchers selected alternative exit gore treatments to test in TTI’s driving simulator. The vertical chevron paired with chevron pavement markings performed consistently well, but none of the alternative treatments performed notably poorly.

Typically, flaggers direct traffic when a lane on a two-lane, two-way road is closed for construction or maintenance, but Texas also uses portable traffic control signals and pilot vehicles to control operating speeds within the lane closure. Researchers conducted field studies to test driver compliance, and overall, only 3 percent of drivers did not comply with the portable traffic control signals and pilot vehicle for both conditions studied (with and without a flagger). Researchers also developed a tool to help pilot vehicle drivers estimate the minimum green time needed to clear the vehicle queue at the portable traffic signal.

The report also discusses two ongoing tasks: coordinating state asset data collection efforts and evaluating rumble devices.