District Variations in Road Curvature in England and Wales and their Association with Road-Traffic Crashes

Abstract

IntroductionReviews of factors affecting road safety on both sides of the Atlantic have concluded that there is abundant evidence that road bends cause traffic collisions, and the sharper the curve, the greater the risk (Bissell et al, 1982;. Typical studies have involved dividing roads into short segments and have compared the number of road-traffic crashes on each road section with a measure of horizontal curvature, finding significant positive relationships between the degree of curve and crash rates. These studies have taken into account other factors that affect crash frequencies such as the length of the segment, traffic flow, carriageway width, edge treatment, vertical alignment (hilliness), and the number of junctions. By holding other risk factors constant in multiple-regression models, the hazardous nature of road bends has been demonstrated to be an independent effect. Examples include studies of modern rural trunk roads in the

Impact of traffic congestion on road accidents: A spatial analysis of the M25 motorway in England

“…Lord and Miranda-Moreno, 2007;Aguero-Valverde and Jovanis, 2008); and the Poisson-gamma model (also known as Negative Binomial model) which is widely used in accident analysis (e.g. Shankar et al, 1995;Milton and Mannering, 1998;Abdel-Aty and Radwan, 2000;Lord, 2000;Amoros et al, 2003;Noland and Quddus, 2004;Kim et al, 2006;Haynes et al, 2007). Poisson-lognormal and Poisson-gamma models have the advantage in that they can accommodate overdispersion in accident data.…”

“…This can also ease the variability of accident frequency from year to year and this is also a common practice used in the previous studies (e.g. Milton and Mannering, 1998;Abdel-Aty and Radwan, 2000;Graham and Glaister, 2003;Haynes et al, 2007). Only accidents recorded as occurring on the M25 motorway are retained.…”

“…However, this variable was found to be statistically insignificant in all models. This may be due to the fact that there is a mixed effect of road curvature (Milton and Mannering, 1998;Haynes et al, 2007), especially on a highly aggregated road segments. This may also be due to the fact that there is not enough variation in horizontal curvature among the M25 road segments.…”

The effects of area-wide road speed and curvature on traffic casualties in England

“…A number of recent studies suggest that area-based models are more appropriate than individual road-based models since the former takes into account system-wide effects (Barker et al, 1999;Noland and Oh, 2004;Haynes et al, 2007). As such, in this paper, the focus is on the area-based accident models.…”

“…An analysis of road curvature (i.e., the quantity of curved roads in an area) and road casualties has been primarily studied by Milton and Mannering (1998) and Haynes et al (2007). Milton and Mannering (1998) Zealand (Haynes et al, 2008), concludes that road curvature has an inverse relationship with fatal crashes on urban settings.…”