Alternative Horizontal Markings along Curved Exit Ramp Terminals to Improve Driver-Safety-Related Performance

Previous investigation has revealed that diverging maneuvers along curved terminals lead to a deterioration in the longitudinal and transversal performances of drivers with respect to linear ones. As a countermeasure, innovative horizontal markings (HMs) may be used to compel drivers to drive more prudently and maintain better vehicle control. In this driving simulation study, the behavioral effects of alternative HMs along curved exit ramp terminals were investigated. Forty-eight voluntary participants drove along randomly assigned exit ramp terminals, the design of which involved combinations of the following input variables: (i) horizontal markings (standard HM1, with internal lane bands HM2, with external zebra stripes HM3); (ii) lighting conditions (day and night); (iii) traffic flow in the motorway (1,000 passenger cars per hour pc/h and 3,000 pc/h), and (iv) ramp terminal connection type (continuous and reverse). Longitudinal (i.e., speed) and transversal (i.e., lateral position and diverging abscissa) behavioral data were collected. HM2 leads to greater improvements in the level of road safety thanks to better longitudinal and transversal driver behavior. However, drivers did delay their exit from the motorway with respect to the baseline condition (HM1) independent of the connection type. No relevant improvements were observed with HM3, apart from speed reductions at the end of the terminal and more centered trajectories when approaching the ramp. Results also show that drivers tended to enter the reverse terminal later than the continuous one (where drivers correctly used the taper), thus revealing that the use of the innovative HMs was not able to compensate for this inappropriate behavior adopted along reverse terminals.