Evaluation of Spatial and Temporal Speed Limit Compliance in Highway Work Zones

Abstract

Typically, speed limits are reduced in work zones to safely accommodate construction activities and motorists on the roadway. This paper presents a methodology to evaluate the temporal and spatial effects of techniques designed to encourage compliance with work zone speed limits. The evaluations were performed over short and long segments within and adjacent to an Interstate construction work zone in suburban Indianapolis, Indiana, with the use of vehicle probe data. Space mean speed was measured by using 13 Bluetooth probe data acquisition stations, which provided a random sample of unique identifiers for approximately 11% of the passing vehicles. These space mean speed data were used to compute a series of comparisons between a day with no enforcement activity and a day with exceptionally high enforcement. During enforcement, the space mean speed decreased by approximately 5 mph throughout the 12.2-mi study segment. Within 30 min after the enforcement detail ended, however, space mean speeds increased, and there was no statistically significant residual impact on the space mean speed. Even at the absolute peak of enforcement, 75% of the probe vehicles exceeded the speed limit in all but one of the segments that had a posted speed limit of 45 mph. In addition, 25% of the probe vehicles exceeded the posted limit by more than 5 mph in all 45-mph segments during peak enforcement. The study is perhaps the largest ever conducted with respect to concurrent enforcement and extensive space mean measurement. The data represent an upper bound on the impact of enforcement activity on work zone speeds and should be of interest to public agencies as they consider compliance techniques.

Best Practices for INDOT-Funded Work Zone Police Patrols

“…For immediate speed reduction, the effect can be easily measured at the scene when police enforcement is ongoing; but for the lasting effect, the measurement is not as straightforward. The spatial lasting effect could be measured downstream of the ongoing police enforcement (20,22,23), while the short term temporal effect could be measured immediately after the police enforcement ends (20,34).…”

“…In a recent study conducted by Wasson et al (34) in Indiana, a very intensive police enforcement ''blitz'' was carried out with 12 enforcement vehicles (marked cars, unmarked cars, unmarked Ford Mustangs, motorcycles, and commercial enforcement units) in a 12-mile rural Interstate work zone. The authors found that the speed rebounded to the enforcement level within about one-half hour, and concluded that there is very little temporal residual effect for ''visible active enforcement.''…”

“…With 13 Bluetooth speed measurement stations, Wasson et al (34) measured average travel speed for 12 sections over a 12-mile long work zone. The space mean speed was calculated for both the beginning of the work zone and the entire work zone, but a speed profile was not provided.…”

Performance Measures for Traffic Signal Systems: An Outcome-Oriented Approach

“…In recent years, a number of technologies have emerged enabling travel time information to be collected on public roads (72)(73)(74)(75)(76)(77)(78)(79)(80)(81)(82)(83)(84)(85)(86)(87)(88). The probe data market is not yet mature enough to be able to effectively measure minor movements and side street delay, except where volumes are exceptionally high.…”

“…The MAC addresses can be matched from station to station to calculate travel times (77)(78)(79)(80)(81). This provides a lower number of samples than from permanent sensors, but there is greater flexibility in setting the locations of the monitoring stations.…”