A fully interactive PC-based STISIM driving simulator was used to test the effectiveness of Intelligent Lane Control Signals (ILCS). The participants were 160 licensed drivers from four age groups: 18-24, 32-47, 55-65, and 70+ years of age. Each participant drove three times in a counterbalanced order. In each trial, after driving five miles in the center lane of a six-lane highway where the speed limit was 65 mph, they encountered five sets of ILCSs that occurred at half-mile intervals. These ILCSs presented (1) 45-mph speed limit messages; (2) 35-mph speed limit messages; (3) a yellow lane closure warning; (4) one of three merge messages that used a diagonal arrow, or words, or dynamic chevrons to indicate that drivers should move from the center lane; (5) a red lane closure warning. Analysis of lane position data showed that the diagonal arrow merge sign was the most effective; participants moved from the center lane 266 feet before reaching the diagonal arrow merge sign, 123 feet before reaching the dynamic arrow merge sign, and 54 feet before the merge sign with words. Analysis of driving speed data indicated that the speed limit signs were effective. Before the 45-mile speed limit was visible, participants drove at 63 mph. When the 45-mph speed limit was visible, they reduced speed by approximately 10 mph. Then on the approach to the 35-mph speed limit, they reduced speed by a further 14 mph-on average, they were driving at 38.7 mph shortly after passing the 35-mph speed limit.

This study is the second in a series investigating rumble strips. The objective was to determine the effect of rumble strips on the stopping performance of sleep-deprived drivers. [The study was nested in a larger fatigue study with components unrelated to rumble strips.] The participants were 20 commercial motor vehicle drivers. Each participant was tested over a twenty- hour period, driving in a driving simulator for one hour in the morning, afternoon, evening and at night. During each drive, the participants encountered two stop-controlled intersections-one with rumble strips and the other without rumble strips. The braking pattern of the drivers was affected by the presence of rumble strips- from the appearance of the first set of rumble strips [218 meters (715.2 ft) from the intersection] until the drivers stopped at the intersection. The mean speed of drivers approaching the intersection with the rumble strips was statistically significantly slower than the mean speed for drivers approaching the intersection without the rumble strips. Though sleep deprivation did not affect the driver's braking patterns on the approach to the intersections, it did affect steering variability throughout the course of the drive.

This was the third in a series of studies investigating various aspects of rumble strips. In this study, to determine the effect of rumble strips on the real-world stopping behavior of drivers, we used a radar gun to collect speed data from over 400 vehicles on the approaches to ten intersections selected from a sample of 274 approaches. We found that, after drivers encountered the first set of in-lane rumble strips, they slowed down earlier on real-world approaches With Rumble Strips than on real-world approaches Without Rumble Strips-the difference was, on average, 2.0 mph to 5.0 mph (depending on vehicle category and type of approach). In addition, speeding outliers were more likely to slow down earlier on approaches With Rumble Strips. The effect of the presence of in-lane rumble strips on stopping behavior was greater for approaches where the driver's view of traffic on the major road is obscured on one or both sides of the road. The study suggests that stop-controlled intersections at which cross-traffic is obscured by manmade structures and/or vegetation on one or both sides of the intersection would be good candidates for implementing in-lane rumble strips. It is worth noting that while in-lane rumble strips are likely to reduce crashes, they cannot eliminate them. Some drivers might still run stop signs and others might misjudge gaps.