In-depth investigation and reconstruction of bus accidents: lessons from a 17 fatalities accident

Abstract

Bus accidents involving rollover are rare but may lead to severe consequences. On the 15th November 2007, at late afternoon, a major accident involving a passenger car and an interurban bus occurred in a motorway in Portugal, resulting in 17 fatalities and 23 serious injuries. Public interest in this accident was magnified and social consequences were aggravated due to the fact that the bus was carrying a study tour of students from a senior university. Following a careful at scene data collection by enforcement agents, the Public Attorney-General decided to establish a multidisciplinary team in charge of reconstructing the accident, finding the manoeuvres involved and explain the contribution of road elements, vehicles and each driver in the mechanisms that produced both the accident and its injuries. This team involved participants from the BT-GNR, (the highway police), the Technical University of Lisbon (IDMEC-IST) and the Portuguese National Laboratory of Civil Engineering (LNEC). It was concluded that the accident started with the car loss of control, followed by its side collision twice with the bus (first with the rear axle, and secondly with the front axle); then, both vehicles ran-off-the-road to the right side of the carriageway, crossed the existing guardrail at the end of the paved shoulder and invaded the steep slope embankment; the car stopped at the bottom of the slope in the ditch. While travelling in the roadside; the bus overturned, resulting in its body failure and the projection of several passengers. Computational simulation tools such as PC-Crash were used to reconstruct the accident. Also Madymo is used to analyse the behaviour of the occupants and to evaluate the injuries of the unbelted passengers as compared with what would have happened if they were effectively restrained by two point belts. Also simulations with three point belts were carried out to evaluate the effect of this improved restraint system under rollover conditions. No serious offences by any driver were detected, as the car was travelling at 120 km/h (the bus at 90 km/h) and both vehicles were in their respective lanes. A definitive explanation for the car driver’s loss was not obtained, due to lack of evidence and inconclusiveness of participant testimonies. As a result of the study carried out, a comprehensive set of factors was identified, that played a role in the transport system failure resulting in the analyzed accident