Evaluation of Green Lights on TMAs

The use of green versus traditional amber lights on Truck Mounted Attenuators (TMAs) was investigated to see if their use could help to improve safety in mobile work zones. Four light color configurations were evaluated via a combination of simulator and field study: amber/white, green only, green/white, and green/amber. The TMAs were used as shadow vehicles representing mobile work zones and were equipped with flashing light bars, an arrow board, and a checkerboard sign with steady light bulbs. Driver behavior measures, including first blinker distance and speed, merge distance and speed, work zone and arrow direction recognition distance, and disability glare were captured in simulator tests. Vehicle speeds as they passed TMAs were recorded in both the simulator and field studies. The simulator study results indicated that the amber/white combination had the highest visibility of work zone but created the highest level of concern with disability glare. The green only configuration yielded the least disability glare but also low overall visibility. The study findings implied an inverse relationship between visibility (awareness of work zone) and arrow board recognition (easy on eyes). The green/amber TMA light configuration performed roughly between the two aforementioned configurations and was the configuration preferred by the participants in a post simulator survey. The field study found that the green only TMA slowed drivers down when they passed the mobile work zone, and lower TMA speeds led to lower vehicle speeds. The results did not point in a single direction for both the simulator and field tests, and all four configurations appear to be viable.