The probability of death in road traffic accidents. How important is a quick medical response?

Abstract

The number of deaths in road traffic accidents in Spain exceeds three thousand people each year. Public authorities have implemented some policies with the aim to reducing this number. Among them, the improvement of road quality standards and some legal changes encouraging careful driving behavior. However, less attention has been focused on one of the issues that may be critical to reducing the number of fatalities caused by traffic accidents: a quick emergency medical care. In this paper, we use a sample of more than 1400 accidents occurred on Spanish roads in May 2004. Our objective is to analyze to which extent a reduction of the time interval between the crash and the arrival of the emergency services to the crash scene is related to a lower probability of death. Our results suggest that a 10 min reduction of the medical response time can be statistically associated with an average decrease of the probability of death by one third, both on motorways and conventional roads.

Introduction

Traffic accidents on Spanish roads are responsible for more than 3000 fatalities per year. With the aim to reducing this number, public authorities have acted in three different ways. First, using the mass media as channels to periodically broadcast traffic campaigns promoting careful driving. Second, there has been a considerable improvement in road conditions in the last few years. For instance, from 1998 to 2004 the number of motorway kilometers available in the national road network raised from 3600 to 12500. Additional efforts have been made to identify and reduce the number of accident black spots. Third, in the last several years some new rules got into force, for example, the mandatory use of safety belts for all occupants of a motor vehicle and the prohibition of using cell phones while driving. These and other related legal norms have been established in the new Score Driving License, which is into force in Spain since July 2006. Italy, France or Germany have similar schemes. All these steps show the concern about road safety and its economic and social impact.

Apart from the legal changes aimed at encouraging careful driving behavior and other changes focused on improving road quality standards, one of the issues that may be critical to reducing the number of fatalities caused by traffic accidents has to do with a quick and efficient emergency medical care. For example, in UK, according to UNECE (2000), about 50% of deaths occur at the site of the crash or during transport to hospital, within less than 1 h after the accident (Haegi, 2002, Coats and Davies, 2002, Charlton and Smith, 2003). Actually, most of the prehospital deaths from accidental injury are due to road traffic accidents, and a portion of them could be preventable with better emergency medical care (Hussain and Redmond, 1994).

The Spanish Traffic General Directory (DGT hereafter) is the institution in charge of all aspects related to road safety in Spain. Let us consider the fatalities/casualties ratio (FCR hereafter), where casualties includes fatalities as well as seriously and slightly injured victims.¹ In 2004, according to the DGT, the FCR in road accidents was 3.3% in Spain, a figure higher than the EU-15 average of 2.3% (UNECE, 2004). However, international comparisons of fatality ratios should be taken with caution, for at least two reasons. First, as it is stated in Elvik and Mysen (1999), the definitions of injury severity vary across countries. Besides, there is evidence of incomplete reporting, especially in the case of injuries, but also to some degree in the case of fatalities. Second, the comparisons should be made once we control for exogenous and endogenous factors affecting fatality ratios, such as the age composition of the population or the vehicle fleet, among others (Page, 2001). Then, a crude comparison of fatality ratios across countries is always debatable.

The objective of this paper is to determine to which extent a faster medical response may be associated with lower fatality risk in Spanish road accidents. To this aim, we link two different databases. One of them contains information on crashes, vehicles and victims. The other one offers, for the first time in Spain, information on the timing of the emergency medical assistance. After the linkage process, our dataset consists of a cross-section of more than 1400 road accidents occurred in Spain in May 2004.

There are several papers in the literature focusing on the relationship between the outcome of a crash and the provision of medical care. From an aggregate perspective, Noland (2003) and Noland and Quddus (2004) point out the improvements of medical care and technology as contributing factors in the reduction of traffic fatalities in industrialized countries in the last several years. At a micro-level, most of the papers analyzing this issue have focused on two factors that can help to reduce fatalities. On the one hand, a quick and accurate crash notification to the emergency services (Brodsky, 1990, Brodsky, 1992, Brodsky, 1993, Evanco, 1999, Clark and Cushing, 2002). On the other hand, the distance from the crash site to a medical centre. This distance can explain geographical variations in traffic mortality rates in areas with different emergency services accessibility (Bentham, 1986, Muelleman and Mueller, 1996, Durkin et al., 2005, Zwerling et al., 2005, Li et al., 2008).

Our paper is a contribution to this literature. We focus on the medical response time, that we define as the time interval between the crash and the arrival of the emergency services to the crash scene. We analyze the potential relationship between this response time and the probability of death. From the methodological perspective, we estimate probit regressions on the outcome of the crash (fatality vs. non-fatality). To isolate the effect of the medical response time from other effects, we include control variables related to the crash and victims’ characteristics.

The rest of the paper is organized as follows. Section 2 provides a description of the data sources used in this paper and the medical response time. Section 3 focuses on the methodology, presenting probit models of the probability of death in a road accident. Section 4 presents the empirical results. A discussion of the main findings is provided in Section 5. Finally, Section 6 offers our main conclusions and some suggestions for future work.