Which factors compromise safety on mountainous roads: A systematic review

Despite the complexity and high crash risk associated with driving on mountainous roads, there is a lack of comprehensive understanding of factors influencing driving performance and increasing risk of crashes on mountainous roads. To address this gap, this study conducts a systematic review by employing the preferred reporting items for systematic reviews and meta-analysis (PRISMA) technique and selected 54 papers for review. The study provides insights into various data collection approaches, including crash history-based studies, naturalistic driving studies, and simulator-based studies, and the performance measures used to analyze driving performance on mountainous roads, including various longitudinal, and lateral measures as well as crash probability. Additionally, the study explores different contributing factors, including drivers, highways, vehicles, and light and weather characteristics, which significantly influence driving performance on mountainous roads. The study reveals a strong correlation between highway characteristics, such as roadway geometry, traffic conditions, road markings, etc., and driving performance. Moreover, the findings highlight a significant impact of age, gender, and driving experience on driving performance. Most importantly, the study highlights significant gaps in literature, which may serve as guides for future research endeavors in safety assessment of mountainous roads. These gaps include absence of consideration of driver education, distraction, and prevalent highway features like sight distance and transition curve length. Furthermore, vehicle types including SUVs, and heavy vehicles have been overlooked in most studies to determine their impact on driving performance. Additionally, the study emphasized the importance of selecting and combining multiple performance measures for a more comprehensive analysis.