A Method to Identify Future Potential of Vehicle Safety Technology

Licentiate thesis, 2012

In the design of a safe road transport system there is a need to better understand the safety challenges lying ahead. One way of doing that is to evaluate safety technology with retrospective analysis of real world crashes. However, by using retrospective data there is the risk of adapting safety innovations to scenarios irrelevant in the future. Also, challenges arise as safety interventions do not act alone but are rather interacting components in a complex road transport system and there exists no linearity between the development of Safety Performance Indicators in traffic and in the final outcome in terms of health losses. This thesis is based on two papers from studies aiming to increase the knowledge in this field by (1) developing and applying a new method to identify future potential of vehicle safety technology in Sweden, and (2) estimate the potential benefits of Autonomous Emergency Braking (AEB) in head-on crashes between passenger cars and heavy-goods vehicles. The first study relates to the need for new prediction models, while the second relates to the need for further understanding how different crash scenarios determines the input and output in different parts in the chain of events leading to a crash, e.g. the integrated safety chain, and thereby affects the performance of safety systems. The key point in study 1 was to project the integrated safety chain in crashes of today into the crashes for a given time in the future. Assumptions on the implementation of safety technologies were made as applied to fatal passenger-car crashes of today. It was estimated which crashes would be prevented and the residual were analyzed to identify the characteristics of future crashes. The study predicts that the number of car occupants killed would be reduced by 53% from 2010 to 2020. Through this new method, valuable information regarding the characteristic of the future crashes could also be found. In study 2 calculations of the available time for AEB depending on crash scenario were done in order to estimate the potential benefits of AEB. The findings indicates that there is a great safety potential in applying AEB in head-on scenarios even late in the integrated safety chain, when the collision is no longer avoidable by steering. It also confirmed that the available time for AEB, and thereby the effect of AEB in delta-v reduction, is highly dependent on the scenarios prior to the point of braking. Application of the combined results from paper 1 and paper 2 can be exemplified in that paper 1 predicts a reduction of loss-of-control scenarios and paper 2 shows that this specific scenario provides the shortest time available for autonomous emergency braking. Thus, there are indications that AEB could have a greater safety potential in the future as loss-of-control scenarios are decreasing over time. Even though more knowledge is required, these interactions and possible systems effects highlights the potential in having an holistic approach when evaluating vehicle safety technologies and their future benefits.