Impact of traffic and road infrastructural design variables on road user safety - a systematic literature review

Road transportation is more favoured as it is less expensive and relatively faster than other modes of transportation. A higher probability of getting involved in crashes reveals its negative impact. However, engineering treatments coupled with safety campaigns and advancements in vehicle technology were slightly successful in reducing crashes. Despite that, road safety is still an issue and one of the significant problems in the world. In an effort to contribute to this growing body of knowledge, this research article tried to facilitate the comprehensive evaluation of past studies, which have attempted to explore the impact of road and traffic attributes on the safety of users. For result synthesis, infrastructural risk variables were classified into four major groups, i.e. exposure, road geometrics, pavement surface condition and traffic control elements, with numerous risk variables within each group. The systemically designed methodology starts with exploring appropriate research literature, followed by analysis, methodology adopted, assessment, limitations and finally ends with result synthesis. Total of 137 high-quality research articles were selected, but only 100 of them were used for conclusion synthesis. The conclusion shows that a variety of infrastructural risk variables influence crashes. However, most of these factors have a combined impact (frication and pavement distress) on road safety rather than individual (speed, curvature, etc.). Additionally, the study found that reallocation or change in infrastructural design is rarely studied in the context of driver behavioural adaptation, thus needs further investigation. Based on reviewed studies and present challenges, some future research directions are also suggested at the end.