External vigilance.

Photographs were used to estimate the incidence of fatal crashes in which passenger vehicles underrode the fronts, sides and rears of large trucks in Indiana during 1993. The photographs were obtained for 98 of the 107 eligible fatal crashes between large trucks and passenger vehicles in 1993. A protocol was developed to judge the presence and extent of underride, the presence of intrusion into the passenger vehicle compartment, and the likelihood of death or serious injury if underride had been prevented. The incidence of fatal underride was compared with the incidence reported in the Fatality Analysis Reporting System (FARS), a census of fatal crashes on public roads in the U.S.A. For the same 107 fatal large truck-passenger vehicle crashes, the incidence of underride reported in FARS was much lower than in the photograph-based study: 6 versus 63%. Photographs contain details absent from police reports, the primary data source for FARS, and thus enable more complete identification of underride crashes. Preventing underride would have substantially reduced the likelihood of death or serious injury in ca 20% of the underride crashes.

Accident Prevention↗

PubMed1998

Conflict analysis for prediction of fatal crash locations in mixed traffic streams.

This paper reports the results of a study that explored the relationship between fatal crashes and conflict rates at mid-block on 14 locations in Delhi, India. All locations had a mix of motorized and non-motorized traffic. The sites were selected to represent low, medium and high fatality rates. The analysis was done in two stages. The first stage used recent 3-year statistics along the entire street. The second stage focused on each fatal crash for mid-block segments on those streets. Peak-hour traffic at 14 selected locations was videotaped. Trained observers recorded traffic compositions at mid-block, average space mean speeds by mode and conflicts by type, reactor mode and cause mode. After converting raw conflict counts to rates, site ranking went from high to low conflict rate sites. The studies showed a weak crash-conflict association. Conflict data for various sites were compared for different combinations of conflicts. The comparison revealed that the presence of only a few non-motorized modes is enough to cause conflicts between motorized vehicles and on-road non-motorized vehicles. The study did not provide a conclusive relationship between mid-block conflicts and fatal crash sites. However, the conflict study provided useful insights into the interaction between different traffic entities in the traffic streams of 14 sites. An important conclusion of this study is that a traffic-planning emphasis on studying conflict rates may not result in reducing fatality rates on urban roads along mid-block segments.

Accident Prevention↗