In search of the severity dimension of traffic events: Extended Delta-V as a traffic conflict indicator

Abstract

Most existing traffic conflict indicators do not sufficiently take into account the severity of the injuries resulting from a collision had it occurred. Thus far, most of the indicators that have been developed express the severity of a traffic encounter as their proximity to a collision in terms of time or space. This paper presents the theoretical framework and the first implementation of Extended Delta-V as a measure of traffic conflict severity in site-based observations. It is derived from the concept of Delta-V as it is applied in crash reconstructions, which refers to the change of velocity experienced by a road user during a crash. The concept of Delta-V is recognised as an important predictor of crash outcome severity. The paper explains how the measure is operationalised within the context of traffic conflict observations. The Extended Delta-V traffic conflict measure integrates the proximity to a crash as well as the outcome severity in the event a crash would have taken place, which are both important dimensions in defining the severity of a traffic event. The results from a case study are presented in which a number of traffic conflict indicators are calculated for interactions between left turning vehicles and vehicles driving straight through a signalised intersection. The results suggest that the Extended Delta-V indicator seems to perform well at selecting the most severe traffic events. The paper discusses how the indicator overcomes a number of limitations of traditional measures of conflict severity. While this is a promising first step towards operationalising an improved measure of traffic conflict severity, additional research is needed to further develop and validate the indicator.

Validation of Simulated Safety Indicators with Traffic Crash Data

“…It can be stated that the ∆V parameter represents the most reliable surrogate safety indicator according to this work. This result is in accordance with recent studies that have proposed an evolution from traditional traffic safety indicators that can be obtained from SSAM software [20]. This new direction of research suggests, in fact, the use of indicators that consider the severity of potential crashes.…”

“…In case study 1, the parameters that showed better correlation (both of Pearson [20] and of Spearman [47]) turn out to be ∆V total and collision; instead, in case study 2, the parameters that are best correlated to the real data are those related to the number of deaths and the number of injuries. This stems from the fact that the area of Paseo de Pereda is an urban area where vehicles are very close to each other.…”

“…Furthermore, Laureshyn et al [20] explain that commonly used surrogate safety performance measures convey "proximity" to a crash and overlook the potential severity of the consequences of a crash. The consequences need to be taken into account in some way [21].…”

“…Crash severity is an extremely important measure [22] and, strangely, the severity of potential crashes was only introduced in surrogate safety indicators in 2017, with the Extended Delta-V method [20]. Delta-V commonly means the variation of the speed vector V of a vehicle after an accident.…”

Perspectives for Surrogate Safety Studies in East-European Countries

“…Some of the original traffic conflict techniques attempt to combine these two severity dimensions by having some subjective score set by an observer. Recently, some objective indicators have been proposed for the same purpose (Alhajyaseen 2015;Bagdadi 2013;Laureshyn et al 2017).…”