Which accuracy levels of positioning technologies do drivers really need in connected vehicle settings for safety?

Based on Global Navigation Satellite Systems (GNSS) and Internet of Vehicles (IoV), collision warning systems can provide drivers specific warning information such as the position of hazardous vehicles. However, positioning technologies vary in accuracy. Highly accurate positioning technologies are theoretically favorable for driving safety but are relatively difficult to use widely due to the high cost. While many researchers compared accuracies of different positioning technologies or explored methods to improve accuracy, few directly investigated the effect of different positioning accuracies for hazardous vehicles on driving safety. The present study conducted a laboratory experiment to explore the effect of four positioning accuracies of hazardous vehicles (i.e., highest: 1.5 m, high: 5 m, medium: 8.5 m, and low: 20 m, each value represented the radius of a circle and the estimated positions of hazardous vehicle were within this circle) and different traffic densities (high: one car per 150 m and low: one car per 1500 m) on driver behaviors. Thirty participants were distributed into high and low traffic density groups. Each participant received auditory warning information, which provided positions of hazardous vehicles relative to the ego vehicle concerning four accuracy levels. Driving safety (i.e., number of collisions and min TTC), driving performance (i.e., brake onset reaction time, steer onset reaction time, and mean deceleration), and subjective workload for warnings with different positioning accuracies of hazardous vehicles were recorded and analyzed. Results suggested the following: 1) Under low traffic density, four positioning accuracies showed no significant differences on driving safety and performance as well as subjective workload. 2) Under high traffic density, the medium positioning accuracy (8.5 m) exerted no significant differences on driving safety and performance compared with the highest positioning accuracy (1.5 m), which had the fastest brake onset reaction time, the least number of collisions, and the largest mean deceleration. Moreover, when traffic density was high, warnings with the highest (1.5 m), high (5 m), and medium (8.5 m) positioning accuracies generated a significantly lower workload than the warning with low (20 m) positioning accuracy. In conclusion, low positioning accuracy (20 m), which was a general accuracy of A-GNSS (no added cost) or GNSS (SPP) (relatively low cost) in dense urban area, was feasible for providing warnings under low traffic density. Medium positioning accuracy (8.5 m), which was the accuracy of A-GNSS (no added cost) in open-sky area, was acceptable for supporting warning systems under high traffic density. These findings have implications for promoting the application of positioning technologies to realize warnings in the near future.