New Crash Countermeasures Found to Reduce Crash Rates and Severity

Featured in Technology Today (Volume 32, Issue 3), a quarterly publication of the Louisiana Transportation Research Center.

In partnership with “Destination Zero Deaths,” DOTD has been continually implementing crash counter- measures. Over the past several years, a few relatively new crash countermeasures were implemented on state highways. These include centerline rumble strips (CLRS) on rural two-lane highways and restriping four-lane undivided roadways (4U) in urban and suburban areas to create three-lane (3T) or five-lane (5T) roadways with center turn lane. To evaluate the effectiveness of these crash countermeasures, LTRC launched a project that investigated the safety impact of center line rumble strips and lane conversions on Louisiana highways.

Before/after image of restriping a typical four- to five-lane highway section [Reproduced from Road Diet Informational Guide]

Spearheaded by Xiaoduan Sun, Ph.D., P.E., and M. Ashifur Rahman, the research team performed a before-and-after crash characteristics analysis, developed crash modification factors (CMFs), and performed benefit-cost analyses for all the investigated safety features.

Mapping it out

Dr. Sun and her team used Google Maps to verify the locations and construction years of each countermeasure. The crash analysis was done by crash severity, manner of collision, user type, time of the day, alcohol involvement, and distracted driver condition. Dr. Sun explained, “To capture all intersection-related crashes, the research team investigated all crashes within at least a 150-ft. radius of intersection. For few intersections with high AADT, crashes that occurred a half mile away from the intersections were also investigated considering potential traffic queues at the intersections.” The team also used original crash reports to further validate and verify crash characteristics in lane conversions.

Recommendation and Results

Dr. Sun and Rahman’s study comes at a crucial time. Despite Louisiana making strides to reduce the number of highway crashes in recent years, the state still ranks worse than the national average in all highway traffic fatality rate measures. Dr. Sun explained, “Based on the results, the project recommends that the state may consider implementing CLRS and lane conversion at locations where targeted crash rate is higher than the state average.”

Overall, researchers found that each crash countermeasure evaluated in this project reduces crashes by number and severity as well as targeted types of crashes for a particular roadway facility:

Centerline rumble strips are an effective measure for rural two- lane highways. The observed crash reductions were 15.1%, 31.2% and 22.1% for total, fatal and injury crashes, respectively.

Based on the small sample size evaluated in this study, the results indicate that lane conversions could be an effective and low-cost crash countermeasure for urban and suburban four-lane undivided roadways with driveway density higher than 36 (studied sections have driveway density varies from 36 to 68 driveways per mile).

To learn more about the results from this study, please contact Dr. Xiaoduan Sun, P.E., at 338-482-6514 or xsun@louisiana.edu.


Photo source: SayCheeeeeese [Public domain], from Wikimedia Commons

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