Evaluation of Innovative Safety Treatments. Volume 4: A Study of the Effectiveness of Motorist Awareness System in Construction Work Zones

In an effort to make work zones safer, the Florida Department of Transportation (FDOT) has developed a new Maintenance of Traffic (MOT) system for work zone traffic control, referred to as Motorist Awareness System (MAS). In addition to traffic control and warning devices used with standard MOT plans, the MAS uses portable changeable message signs, radar speed display units, and regulatory speed limit signs (with flashers) to alert motorists of work zone activities such as lane closures and reduced speed limits. In addition, active enforcement is a critical element of the MAS. Thus, the MAS is intended to reduce travel speeds through work zones. The MAS was implemented as part of construction projects on two segments of Florida interstate highways I-10 and I-95. These segments are a suburban section of I-10 in Baker County, from US 90 to Columbia County line, and a rural section of I-95 in Flagler County from the Volusia/Flagler County line to the Flagler/St. Johns County line. Both I-10 and I-95 are four lane-divided freeways with 70 mph posted speed limits, though I-95 has three travel lanes in one direction at some locations. In order to compare the effectiveness of the Motorist Awareness System, a Comparative Parallel evaluation methodology was utilized. This research analyzed speed data as a proxy variable since higher speeds (and variances) are closely associated with crash risk. Speed data from the following three MOT scenarios were compared to determine the effect of the MAS on travel speeds in work zones: i) Standard Maintenance of Traffic (MOT), ii) Motorist Awareness System (MAS) without police enforcement, and iii) MAS with police enforcement. Measures of effectiveness (MOEs) for this project include differences in average speeds, percent of speeding motorists, and changes in the variability of the speed distribution. Speed studies were conducted at three different locations within each work zone to assess changes in the speed profiles through the work zone: (1) prior to the work zone, (2) in the middle of the work zone, and (3) near the end of the work zone. A total of 179 speed studies were conducted during the control (without MAS) and test (with MAS) conditions. A number of statistical tests were conducted to determine whether the changes observed in the measures of effectiveness are attributable to the use of the MAS or simply due to chance. The results of the statistical tests indicate that the MAS was effective in reducing vehicular speeds through construction work zones. Targeted enforcement resulted in additional speed reductions. The MAS decreased the proportion of motorists traveling over the posted speed limit. Based on these findings, the use of MAS may be a practical countermeasure to reduce vehicular speeds through the work zone, thereby improving safety for both the motorist and the construction worker.