Flaggers protect workers by providing temporary traffic control and maintaining traffic flow through a work zone. They are often the first line of defense to stop distracted, inattentive, or aggressive motorists from intruding into the work area. This project aims to develop an automated intrusion detection system to alert drivers who are unsafely approaching or entering a flagger-controlled work zone. A human factors user needs assessment found maintenance workers preferred a modified traffic signal to feature the alert system due to flagger risks of being in the roadway and drivers failing to stop and remain stopped when presented with the STOP side of the flagger sign. A modified traffic signal that could be operated using a handheld remote was developed. The low-cost embedded electronics on the traffic signal enabled it to track trajectories of nearby vehicles, detect potential intrusions, and trigger audio-visual warnings to alert the intruding driver. Usability testing in a simulated driving test found poor expectancies and stopping rates of the traffic signal-based alarm system compared to a traditional flagger but did demonstrate evidence that drivers may be less likely to stop and remain stopped with the flagger STOP sign than the red ball indicator of the traffic signal. Furthermore, some drivers corrected their initial stopping error after triggering the auditory alarm of the traffic signal. A follow up test found improved performance with the alert system incorporated into an audiovisual enhanced STOP/SLOW flagger paddle. Testing of the developed sensor system found the system capable of simultaneous multi-vehicle tracking (including estimation of vehicle position, velocity, and heading) with a range of up to 60 meters and angular azimuth range of 120 degrees and correctly detecting all test intruding vehicles.
Annually, thousands of highway workers risk serious injury and death from drivers who enter work zones too fast or accelerate after entering the zone and then, because of their excess speed relative to the environmental limitations, have insufficient time to avoid accidents in the zone. Slow-moving vehicles are a problem in reducing traffic flow. This research investigated the effectiveness of a system of pulsing lights, that gave the illusion of movement (Phi phenomenon), in causing drivers to unknowingly synchronize their vehicle speed with the light pulses.
Forty drivers participated: 20 young (10 female, 10 male; 21-42 years) and 20 older adults (10 female, 10 male; 55-87 years). Each participant made 15 passes through the work zone: a control pass with stationary white lights, two control passes with no lights, and 12 passes of test conditions -- 2 colors (red & green) x 3 apparent pulse speeds (-80, 0, & +80 mph) x 2 zone entry speeds (40 & 70 mph).
Age, sex, and zone entry speed differences were found, but overall, (1) backward moving lights (-80 mph) caused drivers to reduce their vehicle speed, (2) forward moving lights (+80 mph) caused drivers to increase their vehicle speed, (3) stationary light and control lights had little or no effect, and (4) green produced stronger effects than red. Backward moving lights caused the greatest slowing in the young while forward moving lights caused the greatest acceleration in the old males and young females.