Extended Use of the Intelligent Speed Adaptation System Based on Sight Limitations to Steady and Transitional Driving Conditions.

Introduction. In road safety, one of the most challenging tasks is speed control. The critical road sections that incorporate with horizontal and vertical curves, providing speed limit information based solely on the posted speed limit is not sufficient to mitigate the risk of collision. In addition, temporary and permanent sight obstruction could represent a major problem for drivers to stop the vehicle before an unexpected obstacle. To address this problem, Intelligent Speed Adaptation for visibility (V-ISA) system has been introduced, which is an in-vehicle system, prevailing three variants (informative, warning and intervening), that supports the driver in adopting a safe speed based on prevailing sight conditions. Previous studies have investigated V-ISA efficiency, functionality, and driver behavior in simple road environment involving only horizontal curves. Nevertheless, adaptation and use of a new in-vehicle system that interacts directly with the driver, requires several scenarios of study, not only over the sections where the system is active but also over those sections at which drivers unconsciously may change their behavior even though the system is not active. Objective and methodology. The scope of this study is to implement the novel V-ISA system to more realistic driving conditions involving traffic flow, integrating curves with reduced visibility and transitional sections. For this aim, (i) informative (V-ISA-I) and (ii) intervening (V-ISA-III) variants of the system are applied, where V-ISA-I informs the driver through color bars while V-ISA-III intervenes on the acceleration pedal, inhibiting driver speeding when safety speed is reached. This experimental study was conducted in a driving simulator involving 32 drivers. Their longitudinal and transversal behavior were measured in steady and transitional driving conditions under two different traffic flow levels. Results and conclusions. Drivers shown a positive longitudinal and transversal response in the use of the V-ISA system over steady sections. Compelling drivers to maintain safer operating speed at sections with sight limitations. On the other hand, at transitional sections, results demonstrate that drivers do not depict longitudinal behavior changes performing diverging maneuvers while using the V-ISA system. Furthermore, V-ISA influences drivers transversal behavior, evidencing changes in merging and diverging abscissa. Although this study showed positive findings in the V-ISA implementation, further analysis is required for acceptance and its complete workability. Adaptation of the system to multiple road scenarios, as well as its integration among other Advanced Driver Assistance Systems (ADAS) such as Adaptive Cruise Control (ACC), could lead to complete driving assistance and reduced level of risk while driving.