The objective of the current study was to (1) use a driving simulator to test simulated roadway elements to determine their effectiveness in capturing driver attention and fostering compliance in work zones and then (2) in a field test evaluate the on-road effectiveness of the elements identified in the driving simulation study. This two-pronged (driving simulation and field study) investigation of driver behaviour in work zones contributes basic and applied knowledge to our understanding of work zone safety. One hundred and sixty licensed drivers from four distinct age groups participated in the driving simulation study. There were 40 participants in each of the four age groups–younger (18 to 24 year olds), middle age (32 to 47 year olds), older (55 to 65 year olds), and seniors (70 years or older). There were 20 males and 20 females within each age group. All 160 participants were licensed drivers. The four age groups included drivers from the metro and non-metro regions and each was paid $50 for his or her participation. In the driving simulation portion of this study, we used a fully interactive PC-based STISIM driving simulator with an automative-style seat that faced a bank of three 21-inch monitors. Three PCs generated the virtual environment presented on the monitors. Participants drove 10 miles on a two-lane bidirectional highway before they encountered the first warning sign in each of the three drives (conditions). The layout of the control condition is shown in Figure 1. The layout of the work zone area and the distance between the warning signs was the same for each of the three conditions; however, the type or content of the warning signs was changed. In the second condition, each participant encountered four sets of warning signs before he or she approached the work zone, with the (1) “ONE LANE ROAD AHEAD”, (2) combined warning signs of “Flagger Ahead” figure and 45-mile speed limit, (3) combined warning signs of 45-mile speed limit and a dynamic speed limit trailer, which indicated the driving speed of the car within a zone (ahead of the trailer), and (4) “BE PREPARED TO STOP” situated 50 feet before portable rumble strips. In the third condition, flashing LED lights were added to the perimeter of the “ONE LANE ROAD AHEAD” sign and an auditory warning horn sounded when participants exceeded the 45 mph speed limit on their approach to the dynamic speed limit sign. Analysis of the effectiveness of LED flashing lights: No statistically significant differences in mean speeds were found between the conditions on the approach to the first warning sign, indicating that the LED lights did not contribute to reduced driving speed. Analysis of the effectiveness of the horn: The results indicate that there is a statistically significant effect of the warning horn on the speed reduction after the dynamic speed limit sign. However, the horn did not have a continued, pronounced effect into the work zone. It is important to remember that the horn is intended to capture the attention of driver outliers in work zones. The results of this analysis reveal that the horn did capture the attention of outlier drivers and led to statistically significant reductions in driving speed in comparison to those driver outliers who did not hear the horn. The results indicate that nine participants left their lane to avoid experiencing the rumble strips for at least one of the conditions. Of the nine, three participants left their lane to avoid the rumble strips in both conditions, while the other six left the lane to avoid the rumble strips only once. If the opposing lane is closed to oncoming traffic, it is not dangerous for drivers to leave their lane in a flagger-controlled work zone. If, however, the opposing lane is not closed to oncoming traffic, then in-lane transverse rumble strips could foster unsafe driving behaviour. While this research reveals that rumble strips capture driver attention, the data also reveal that some drivers engage in potentially unsafe driving behaviour to avoid the rumble strips. In summary, we found that the new set of elements is more effective than the elements currently used to reduce driving speeds on the approach to a flagger-controlled work zone. We found no difference in mean driver speed in response to the sign with an LED presence. We found that the dynamic speed display coupled with the horn is more effective than the dynamic speed display alone. FIELD STUDY: The cognitively engaging elements identified as effective in the driving simulator study were tested in a field operational test. One field test of the cognitively engaging/attention-grabbing devices in an active work zone was conducted in Spring Valley, MN on CSAH 8. The work zone was managed by Rochester Sand and Gravel which was performing a full-depth reclamation and resurfacing of 4.1 miles of CSAH 8 north of Spring Valley. Data were collected over an eight-day period. During that time, the research team set up and deployed two different work zone layouts alongside the active work zone on one approach. The first, referred to as base, was the minimum standard setup following Minnesota Manual on Uniform Traffic Control Devices (MN MUTCD) guidelines. This setup was supplemented with additional radar sensors, manufactured by Smartmicro, to gather data from the approaching vehicles during the base conditions. The second setup deployed, referred to as the experimental layout in this report, included additional signs and attention getting devices (Horn, Rumble Strips, Speed Trailer) identified as effective during the driving simulator experiment. This layout was also instrumented with additional radar sensors and cameras to gather data on the approaching vehicles. An earlier field test of the new proposed work zone layout in an active work zone was conducted in Pine City, MN on State Highway 70. The work zone was active over the course of four days. Unfortunately, a combination of short work zone working periods as well as low traffic volumes did not allow for the collection of a statistically secure sample of speeds. Interestingly, the results from the two tests are very comparable. This finding reinforces the observations collected and conclusions reached because the two sites were located very far from one other, the data were collected over a different time period, and the sites were operated by completely different work zone crews. In summary, the field test revealed that all but one of the elements identified in the experimental driving simulator study were effective. In particular, the findings revealed that a combination of the speed trailer and horn barrel is effective in reducing the overall speed of vehicles approaching the work zone. The portable rumble strips, however, did not generate any significant speed reduction, although a definitive evaluation of the portable rumble strips would have required a test of the strips in isolation and not when placed downstream of the speed trailer. Unfortunately, such an experiment was not in the scope of this study. Apart from the portable rumble strips, the field test revealed that the new experimental layout practically eliminated high-speed outliers in addition to its success in reducing driver approach speed to the flag operator. (Author/publisher)
Abstract