Studies to determine the operational effects of shoulder and centerline rumble strips on two-lane undivided roadways.

Finley, Melisa D.; Funkhouser, Dillon S.; Brewer, Marcus A. · 2009 · ROSA P / Texas Transportation Institute

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Summary

This study investigates the operational effects of shoulder rumble strips (SRS) and centerline rumble strips (CRS) on two-lane undivided roadways, specifically addressing concerns regarding vehicle lateral placement and driver recovery capabilities. While previous research established that SRS and CRS significantly reduce run-off-road and head-on crashes, questions remained regarding whether these countermeasures adversely affect vehicle positioning within travel lanes or provide sufficient warning time for errant drivers to correct their trajectory. The research aimed to determine if CRS cause vehicles to shift excessively toward the shoulder, if SRS cause shifts toward the centerline, and what minimum shoulder width is required for drivers to recover after being alerted by SRS. The researchers employed a mixed-methods approach comprising field studies and closed-course experiments. Field studies analyzed vehicle lateral placement data collected from various sites equipped with CRS, SRS, or both, including locations with narrow lane widths (10 ft) and varying shoulder widths. These sites were compared against control sites without rumble strips. Additionally, closed-course studies utilized an instrumented vehicle to simulate distracted driving scenarios. Participants performed secondary tasks while driving over rumble strips to measure reaction times, departure angles, and lateral corrections. The experimental design accounted for variables such as vehicle type, shoulder width, and the lateral offset of the rumble strips from the edgeline. The findings indicate that CRS on two-lane undivided roadways with lane widths as narrow as 10 ft do not adversely impact lateral vehicle placement; in fact, drivers positioned their vehicles closer to the lane center at sites with narrow shoulders (1–2 ft). Similar stabilizing effects were observed at sites with both edgeline and centerline rumble strips. Regarding SRS, those located near the edgeline (7–9 inches offset) appeared to shift vehicle paths closer to the centerline, whereas SRS located 35 inches from the edgeline had no significant impact on lateral placement. The closed-course studies determined that lateral offsets positioning the center of 16-inch SRS in the middle of shoulders at least 4 ft wide provide sufficient remaining shoulder width for the 85th percentile distracted driver to correct an errant trajectory before leaving the paved surface. The study concludes that CRS are operationally safe for narrow lanes and do not induce erratic maneuvers or excessive lateral shifts toward the shoulder. For SRS, placement near the edgeline maximizes recovery area but may influence lane positioning, while larger offsets mitigate lateral shifts but reduce available recovery space. The research provides specific guidelines for minimum shoulder widths and rumble strip offsets to balance safety benefits with operational constraints. These findings support the continued implementation of rumble strips on two-lane undivided highways, offering evidence-based recommendations for optimizing their placement to minimize potential negative operational impacts while maximizing crash reduction benefits.

Key finding

Centerline rumble strips do not adversely impact lateral placement on narrow lanes, and a remaining shoulder width of at least four feet provides sufficient recovery space for the 85th percentile distracted driver to correct errant trajectories.

Methodology

mixed_methods

Sample size: 101

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• perceptual countermeasures