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Purdue University, in partnership with Ver-Mac and the Indiana Department of Transportation, conducted a study on the effectiveness of using Presence Lights & Work Zone Digital Speed Limit Trailers to increase motorist awareness & overall work zone safety.



Here are some encouraging key findings from the study that support the further development of presence lighting and speed limit trailers in night-time construction zones to reduce vehicle speed:

• The results showed that median speeds decreased by up to 13 mph from 11 PM to 7 AM with the deployment of presence lighting and digital speed limit trailers, compared to without these devices deployed. These results are consistent with previous presence lighting studies that showed similar speed reductions of 4 to 7 mph.

• Increased compliance with the 55-mph speed limit was observed when presence lighting and digital speed limit trailers were deployed.

An earlier study, lead by the North Carolina Department of Transportation (NCDOT) drew similar conclusions after studying motorists driving through work zones on a four-lane interstate and a four-lane freeway.

An interim report of “An Evaluation of the Effectiveness of Digital Speed Limit Signs and Work Zone Presence Lighting on Speed Compliance During Lane Closure Operations” revealed:

• The presence of digital speed limit signs combined with lighting successfully reduced motorists’ speed. On average, speeds were reduced by 12 to 14 mph

• Digital speed limit signs with flashing beacons had the biggest influence on work zone speed limit compliance

Making Work Zones More Secure