Driver Response to a Dynamic Speed Feedback Sign at a Freeway Exit Ramp Considering the Sign Design and Installation Characteristics

Abstract

Research was conducted at a freeway exit ramp with significant horizontal curvature to evaluate the effectiveness of dynamic speed feedback signs (DSFSs) as a speed reduction countermeasure. Several aspects of the DSFSs were evaluated, including display size, border type, lateral installation position, and vehicle detection range. Three different full-matrix DSFSs were utilized, which included 15-in. display panel with yellow border, 18-in. display panel with yellow border, and 18-in. display panel with no border. Each sign was individually installed and tested at identical locations near the start of the exit ramp curve, in both the traditional right-side-mount and an alternative forward-mount within the exit gore area. Speed data and message activation location were collected for vehicles approaching and entering the curve across the various sign test conditions. Overall, the presence of a DSFS positioned near the start of the curve resulted in curve entry speeds that were, on average, 3.5 mph lower than without a DSFS present. The lowest curve entry speeds were observed for cases in which the message activated when vehicles were within 250 to 400 ft of the curve. Interestingly, earlier message activation did not contribute to further speed reductions, although later activation substantially diminished the speed reduction effects. With regard to DSFS lateral position, both the side-mounted and forward-mounted DSFS installations resulted in similar curve entry speeds. Furthermore, there were no discernable differences in curve entry speeds between the 15- and 18-in. display panels, although the inclusion of a yellow sign border had greater speed reduction effects.

Evaluating Driver Response to a Dynamic Speed Feedback Sign at Rural Highway Curves

“…and in display size (15 versus 18 in.). However, despite the differences in size, no differences in the speed reduction effects were observed between the two signs during prior evaluations at freeway exit ramp curves (26). The radar detection unit was embedded in the sign face and had a detection range of approximately 400 ft for passenger cars and up to 600 ft for heavy vehicles.…”

Assessing the Effects of Interchange Warning Systems on Driving Risk: A Driving Simulator Study

“…Mahmud et al conducted research on the layout and design of dynamic message signs in the warning system. Mahmud et al [10,11] analyzed the efects of dynamic message signs at diferent positions on curves with radius and investigated the efects of dynamic message sign borders, display text size, and roadside placement distance on the warning system. Gates et al [12] studied the infuence of diferent placement distances and display content on various vehicle types while Cui et al [13] classifed the collision risk on-ramps based on the analysis of vehicle trajectories and collision risk and guided drivers to pass through the ramps in an orderly manner by issuing information on the message board.…”

Driver Response to a Dynamic Speed Feedback Sign at Speed Transition Zones Along High-Speed Rural Highways

“…This targeted messaging strategy can be personalized in nature, and it is particularly effective in reducing excessive speeding (4)(5)(6)(7). It has been widely used and successful in a variety of settings, including work zones on both freeways and rural highways (8,9), school zones (10), horizontal curves (10)(11)(12)(13), high-speed arterials (10,12,14,15), freeway exit ramps (5)(6)(7), and speed transition zones (4,10,16,17). However, the use of speed feedback signs as a speed reduction measure at speed transition zones on rural highways is not well documented, and the effectiveness of these devices in such contexts remains unknown.…”

“…This device utilizes radar to detect the speed of the approaching vehicles and shows the speed value and/ or a speed warning message on a digital display along with targeted messages such as ''SLOW DOWN,'' ''TOO FAST,'' ''SPEED LIMIT XX.'' This targeted messaging strategy can be personalized in nature, and it is particularly effective in reducing excessive speeding (4)(5)(6)(7). It has been widely used and successful in a variety of settings, including work zones on both freeways and rural highways (8,9), school zones (10), horizontal curves (10)(11)(12)(13), high-speed arterials (10,12,14,15), freeway exit ramps (5)(6)(7), and speed transition zones (4,10,16,17).…”