Three prototype Automatic Truck Rollover Warning Systems (ATRWS), located in Virginia and Maryland, were evaluated over three years to assess how the ATRWS performed and to determine the cost-effectiveness. More specifically, the requirements of this evaluation were to (1) evaluate performance and maintenance requirements, (2) evaluate the effectiveness of the ATRWS on speed reduction of detected trucks traveling at or near their rollover speed or maximum safe speed, and (3) evaluate any improvements in safety resulting from the systems. Based on truck classification and speeds as measured by the ATRWS, it was concluded that these systems do affect truck speed reduction. The results showed that for all three ATRWS sites (five lanes total), a speed reduction was observed when the fiber optic sign was activated. The results also showed that this speed reduction was usually higher than the speed reductions of trucks that did not activate the sign. In fact, for the first and second evaluation periods, an overall 29.0 and 21.7 percent speed reduction from Stations 2 to 3 and Stations 5 to 6 was observed. These percentage speed reductions equate to approximate speed reductions at the Springfield, McLean, and Beltsville ATRWS sites of 4.6 km/h (2.9 mph), 3.9 km/h (2.4 mph), and 2.3 km/h (1.4 mph) for the first evaluation period. The second evaluation period had similar speed reductions.
