Ming-Heng Wang

Downstream effects of speed photo-radar enforcement and other speed reduction treatments on work zones

The effects of automated speed photo–radar enforcement (SPE) and traditional speed reduction treatments (speed feedback trailer, presence of police vehicles with emergency lights on and off, and combinations of the speed feedback trailer and police presence) on speed were studied at a location 1.5 mi downstream of the actual treatment (spatial effects). Three data sets from two Interstate highway work zones were used. Field data consistently showed significant spatial (downstream) effects for SPE. The combination of speed feedback trailer and police vehicle with emergency lights off had downstream effects in some cases but to a lesser degree than SPE. Other treatments showed no significant downstream effects. For free-flowing traffic, SPE reduced the average downstream speed by 2 to 3.8 mph for cars and by 0.8 to 5.3 mph for trucks. Also, SPE reduced speeding cars by 7.1% to 23.4% (except for cars in median in Data Set 1), and speeding trucks by 4.2% to 48.3% (except for trucks in shoulder in Data Set 3). For the general traffic stream, SPE reduced the average downstream speed by 1.1 to 2.9 mph on cars and by 0.9 to 3.3 mph on trucks. When SPE was used, the percentage of speeding cars and trucks in the general traffic stream was reduced by 2.9% to 28.6%, and by 7.5% to 36.1%, respectively. SPE also reduced the percentage of cars in the general traffic stream exceeding the speed limit by more than 10 mph in virtually all cases, and eliminated such trucks in all but one case.

Closed-Course Test and Analysis of Vibration and Sound Generated by Temporary Rumble Strips for Short-Term Work Zones

Driver distraction and speeding are two contributors to crashes in construction and maintenance work zones. Rumble strips can be effective and have been used in some states to alert drivers to reduce speed in advance of some change in the driving situation, such as at intersections. Previous research has examined the potential of using temporary rumble strips in advance of work zones. The purpose of this research was to compare the attention-getting characteristics of several temporary rumble strips with permanent rumble strips. Two types of devices were tested and compared with permanent rumble strips: portable plastic rumble strips and adhesive rubberized polymer rumble strips. These devices were tested for their ability to generate steering wheel vibrations and in-vehicle and roadside sound. Analysis revealed that the portable plastic rumble strips were more effective on cars than on trucks for generating in-vehicle vibration and increasing the in-vehicle sound level. Further, they were generally better than the adhesive rumble strips in matching the characteristics of the tested permanent rumble strip. This was also true for the configurations that contained fewer than six portable plastic rumble strips. If the vibration and sound generated by the permanent rumble strips is considered the standard performance, various configurations of the portable plastic rumble strips can be implemented in short-term work zones and provide results similar to those of permanent rumble strips.

A Closed-Course Feasibility Analysis of Temporary Rumble Strips for Use in Short-Term Work Zones

This research was conducted to determine how best to incorporate portable rumble strips into traffic control plans for short-term work zones. One objective of the research was to provide guidance on how existing traffic control plans could be amended to include provisions for the evaluated devices. This research focused on rumble strips that were considered beneficial for any type of work zone where the duration is one day or less. The tests on the portable rumble strips were conducted on a closed roadway surrounding the Kansas Speedway in Kansas City, Kansas, and in a closed park-and-ride parking facility in Lawrence, Kansas. The rumble strips tested in this study were two different types of reusable temporary rumble strips made out of steel with a rubber bottom and four generations of plastic rumble strips. From this study the best solution for most short-term work zones would be the latest generation of plastic rumble strips tested. The earlier generations did not perform as well as the fourth generation especially at 60 mph (96.6 km/hr). The steel rumble strips also hold some promise; however, the structural integrity of the steel rumble strips is an issue that needs to be addressed.

Effects of Innovative Portable Plastic Rumble Strips at Flagger-Controlled Temporary Maintenance Work Zones

This study evaluated the effects of portable plastic rumble strips (PPRSs) on speed reduction and drivers’ behaviors in advance of flagger-controlled work zones. Travel speed data were collected at three two-lane highways with temporary (less than a day) maintenance activities, at which standard flagger traffic control was set up with or without the implementation of PPRSs. Drivers’ reactions to the PPRSs, such as changing lanes and braking in the vicinity of the PPRSs, were also investigated when the PPRSs were in place. The results showed that drivers became more cautious because of the PPRSs. The PPRSs reduced car mean speeds by 9.7 to 22.2 km/h (6.0 to 13.8 mi/h). They also decreased the 85th percentile of car speeds at two field test sites. It was observed that 30 to 80% of all drivers activated their brakes when they approached the PPRSs close to the flagger. In addition, about 5% of car and truck drivers swerved around the PPRSs. This indicates that additional signing or other supplemental traffic devices would be needed when the PPRSs are implemented.

Safety and headway characteristics in highway work zones with automated speed enforcement

This paper investigated the headway distribution of platooning vehicles in work zones with and without automated Speed Photo Enforcement (SPE). Data from two work zones were collected and analyzed. The portion of vehicles traveling with a very short headway (less than 0.7 sec) was also examined. In addition, the behavior of vehicles near the law enforcement vehicles was analyzed in terms of applying brakes and changing lane in one of the work zones. The results indicated that the mean headway of cars in the median lane significantly increased in both work zones when the SPE van was present compared to the base condition. For trucks, the mean headway increase was significant only in the shoulder lane when the SPE was present. This is a beneficial effect and indicates that drivers had a longer time to react to the lead vehicles. It was also found that the proportion of cars traveling with a very short headway in the median lane significantly decreased when a SPE van was present at one work zone (I-64). In the shoulder lane, no very short headway was observed when SPE was implemented. The difference in braking behavior was not significant when SPE was compared to police car presence. However, lane changing behavior was significantly different for cars traveling in the median lane and also for trucks traveling in the shoulder lane. The proportion of cars changing lanes was 5 percent with a police car present and increased to 8 percent when the SPE van was present. A significant number of trucks changed lanes from the shoulder to the median when the police car was present to comply with state law.