Driver Understanding of Sequential Portable Changeable Message Signs in Work Zones

In work zones, drivers do not slow down in response to conventional signs. Changeable-message signs (CMSs) equipped with a radar unit can be used to display specific warning messages to speeding drivers. The radar unit detects the speed of each vehicle entering the work zone and can be programmed to activate the CMS if the speed of the vehicle exceeds a preset threshold value. A two-phase longitudinal study was conducted. The first phase, conducted by Garber and Patel, examined the short-term effectiveness of the CMS with radar in reducing vehicle speeds in work zones. The second phase, some of the results of which are presented, evaluated the influence of the duration of exposure of the CMS with radar on its effectiveness in reducing speeds in work zones. Speed and volume data for the population were collected at the study sites by automatic traffic counters placed at the beginning, middle, and end of each work zone. In addition, the speeds of individual drivers who triggered the CMS by exceeding the threshold speed were also recorded (using a video camera) at two other locations within the work zone for several weeks and analyzed. The results of the study indicated that the duration of exposure of the CMS does not have a significant impact on speed characteristics and driver behavior. Therefore, the CMS continues to be effective in controlling speeds in work zones for projects of long duration. The results also indicated that the CMS with radar reduces the probability of speeding at work zones and that this effect is maintained for at least up to 7 weeks.

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Evaluating Speed-Reduction Strategies for Highway Work Zones

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1824-06 ◽

2003 ◽

Vol 1824 (1) ◽

pp. 44-53 ◽

Cited By ~ 10

Author(s):

Chunyan Wang ◽

Karen K. Dixon ◽

David Jared

Keyword(s):

Traffic Control ◽

Statistical Tests ◽

Work Zones ◽

Control Zone ◽

Novelty Effect ◽

Speed Reduction ◽

Reduction Strategies ◽

Changeable Message Signs ◽

Message Signs ◽

Over Time

Research was conducted to identify the potential of fluorescent orange sheeting, innovative message signs, and changeable message signs with radar for reducing speeds in highway work zones. The study investigated the effect of each strategy immediately after implementation (immediate effect) as well as several weeks after implementation (novelty effect). In addition to the overall effect of each strategy on all vehicles, the study included the effect on specific vehicle types during various lighting conditions. The researchers collected traffic data before, immediately after, and 2 or 3 weeks after implementation of each strategy (3 consecutive weeks for the changeable message sign). They collected data upstream of the temporary traffic-control zone, in the advancewarning area, and adjacent to the active work area. The researchers used various statistical tests to evaluate the significance of speed changes from phase to phase and adjusted vehicle speeds with the upstream speed changes over time. The study indicated that fluorescent orange sheeting and innovative message signs help reduce speeds at highway work zones (with diminished influence over time). Moreover, both strategies influence vehicle speeds more during the day than at night. Drivers of passenger vehicles tended to decrease their speeds more than did truck drivers. Changeable message signs with radar significantly reduced the vehicle speeds in the immediate vicinity of the sign and did not demonstrate a novelty effect.

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