Drivers’ noncompliance with the posted speed limit reductions on rural-to-urban freeway transition zones is a recurrent problem in Indiana and other states. Speed-reduction treatments, such as pavement markings and active signing, aim to solve this issue. Optical speed bars, longitudinal speed reduction markings, and speed feedback signs were identified as the most promising speed-reduction treatments for experimental implementation in Indiana. Probe-vehicle-based speed data for 1 year was acquired on selected freeway segments to measure the speed effect. A set of fixed-effects linear regression models were used to estimate the effect of speed-reduction treatments on three key speed behavior characteristics—average speed, 90th speed percentiles, and speed variability. Optical speed bars together with speed feedback signs are a promising combination of treatments. While this and other traditional speed-reduction treatments show promise, their influence area is limited to a portion of target road segments. Therefore, future speed management needs to consider other speed-reduction treatments, particularly automated and area-wide speed enforcement, to maintain reduced speeds inside urban areas.

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The following URL shows optical speed bars implemented on I-70 WB near Indianapolis from 1.09 miles east of Post Road to 0.75 miles east of Post Road: The pavement markings were supplemented with a speed feedback sign located on the outside shoulder. The estimated speed reduction is 2.8 mph, which spans 2.4 miles. A similar treatment implemented on I-64 EB, from 5,120 feet west of SR-64 to 3,320 feet west of SR-64, produced a 3.5-mph speed reduction spanning 2.0 miles.

The following URL shows longitudinal speed reduction markings implemented on I-65 NB near Indianapolis from 2,080 feet south of Thompson Road to 280 feet south of Thompson Road: The pavement markings were supplemented with two speed feedback signs located on the median and outside shoulder. The estimated speed reduction is 1.1 mph, which spans 2.8 miles. A similar treatment implemented on I-65 SB, from 0.74 miles south of Old SR-311 and ending at 1.08 miles south of Old SR-311, produced no statistically significant changes in speed behavior.


suburban freeways, speed management, pavement markings, active signing, probe-vehicle-based speeds, panel data analysis, speed transition zone, urban freeway, speed control

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, IN

Date of this Version