Geometric Constraints and Visual Field Related to Speed Management

Abstract

This study investigates the challenges inherent in rural arterial roads and highways connecting small towns and cities in Indiana. Despite their pivotal role in transportation and development, these roads often experience a high frequency of traffic accidents attributed to speeding, particularly at transition areas from high-speed to low-speed roads. To address this issue, this study investigated cost-efficient and effective speed management countermeasures. This study emphasized the importance of considering cost-efficient and effective speed management strategies, with a focus on roadside vegetation and lane widths near small-town entrances on arterial roads and highway ramps. Proposing four countermeasures for each scenario—such as large spacing bush, small spacing bush, hedge, and narrow lane width for arterial roads or a delineator for highway exit ramps—the investigation employed driving simulator studies involving sixty human subjects to assess the individual and interactive effects of these interventions. The results on driving speed and deceleration rate show that specific combinations of narrow lanes and roadside vegetation were effective in mitigating speeding on arterial roads and highway ramps, especially during the transition zones. The study also revealed that the speed reduction effects of these countermeasures do not persist in post-countermeasure segments, which reduce the boarder impacts of these interventions. The research underscores the importance of a targeted and context-aware approach in selecting and implementing speed management measures and emphasized the need for tailored interventions based on the specific characteristics of each roadway type and scenario.