Directional Rumble Strips for Reducing Wrong-Way-Driving Freeway Entries

Project summary:

Wrong-way driving on freeways has been identified as a serious traffic safety problem. Drivers who make wrong-way entries onto freeways pose a serious risk to the safety of other motorists and themselves. This study investigated the feasibility of a novel design of directional rumble strips (DRS) to discourage wrong-way entries onto freeway exit ramps as well as identified proper implementation locations.

In phase 1, field tests completed in fall 2015 evaluated the effectiveness of five types of DRS concept designs. The tests included both sound and vibration analysis of five patterns with different configurations. Three patterns (Pattern C, Pattern D Configuration 3, and Pattern E) were recommended for future verification and final implementation. Over the last 6 months, the verification field tests were conducted by the Auburn University team to evaluate the effectiveness of those three recommended DRS patterns.

In November 2016, further field tests were conducted to collect sound and vibration data generated by three DRS patterns at the National Center for Asphalt Technology (NCAT) at AU. Statistical analysis was conducted to examine the difference between right-way and wrong-way direction for both sound and vibration. The results were consistent with prior results. Pattern C generated significant different sound and vibration in right-way and wrong-way direction at speeds from 10 to 25 mph. Pattern E showed significant statistical vibration difference at 45 mph.

For sound and vibration data, waveforms in time domain were used to identify the relative loudness of sounds in air and the severity of the vibration as perceived by the driver. In addition, Fast Fourier Transform was used to evaluate the vibration amplitude as a function of frequency. This analysis was performed in the frequency domain to gain a deeper understanding of the vibration data. The results implied that the difference in sound and vibration between right-way and wrong-way directions was not significant when driving at the same speed in both directions. However, because average speed of right-way and wrong-way driving will be different at the specific locations of off-ramps where DRS is installed, DRS Pattern C, Pattern D Configuration 3, and Pattern E can achieve the goal to generate larger sound and vibrations for wrong-way drivers.

An implementation guide is needed for transportation agencies to identify proper locations for installing these patterns to achieve the best performance based on length and type of off-ramps. Three off-ramps were selected for the experimental implementation. Each location has a specific ramp design feature that works well with each of the design patterns.

For next steps, a research proposal has been developed and submitted to ALDOT for the implementation of DRS patterns at the selected three off-ramps. Field studies and before-and-after comparisons will be conducted to evaluate the operational effectiveness of DRS and help finalize the guidelines for implementation of DRS.

• OST-R summary report for this project (PDF)