Impact of Pavement Roughness on Traffic Safety under Heterogeneous Traffic Conditions

Abstract

Highway safety is a major priority for the public and for transportation agencies. Pavement roughness directly affect ride quality, and indirectly contribute to driver distraction, vehicle operation, and road traffic accidents. This study focuses on analysing the influence of pavement roughness on traffic safety using data on dual and single carriageway operated under heterogeneous traffic conditions in South-west, Nigeria. Two main types of data were collected for the years between 2012 and 2015: traffic crash data was obtained from the Federal Road Safety Commission (FRSC) and International Roughness Index (IRI) data from the Pavement Evaluation Unit of the Federal Ministry of Works, Kaduna. Crash road segments represented 63 percent of the total length of roads. IRI values for crash and non-crash segments were close to each other, suggesting that roughness is not the only factors affecting number of traffic crashes but a combination with other factors such as human error, geometric characteristics and vehicle conditions. Crash severity was categorized into Fatal, serious and minor injury crashes. In all cases, the total crash rate increases with increase in IRI value up to a critical IRI value of 4.4 and 6.15 for Sagamu-Ore road and Ilesha-Akure-Owo road respectively, wherein the crash rate dropped. This is a key conclusion that provides empirically derived thresholds for safety concerns. If transportation agencies keep their road network below these critical pavement conditions, the crash rate would largely decrease. It is concluded that ride quality does not directly affect traffic crash rate.

Keywords

• pavement conditions, traffic safety, international roughness index, crash rate, carriageway