Citation

Koglbauer I, Holzinger J, Eichberger A, Lex C. Traffic Injury Prev. 2018; 19(3): 332-337.

Affiliation

Institute of Automotive Engineering, Graz University of Technology , Inffeldgasse 11/II, 8010 Graz , Austria.

Copyright

(Copyright © 2018, Informa - Taylor and Francis Group)

DOI

10.1080/15389588.2017.1407411

PMID

29227692

Abstract

OBJECTIVE: This study investigated drivers' evaluation of a conventional autonomous emergency braking (AEB) system on high and reduced tire-road friction, and compared these results to those of an AEB system adaptive to the reduced tire-road friction by earlier braking. Currently automated systems such as the AEB do not adapt the vehicle control strategy to the road friction, e.g. on snowy roads. Since winter precipitation is associated with a 19% increase in traffic crashes and a 13% increase in injuries compared to dry conditions, the potential of conventional AEB to prevent collisions could be significantly improved by including friction in the control algorithm. Whereas adaption is not legally required for a conventional AEB system, higher automated functions will have to adapt to the current tire-road friction since human drivers will not be required to monitor the driving environment at all times. For automated driving functions to be used, high levels of perceived safety and trust of occupants have to be reached with new systems. The application case of an AEB is used to investigate drivers' evaluation depending on the road condition in order to gain knowledge for the design of future driving functions.

METHODS: In a driving simulator the conventional, non-adaptive AEB was evaluated on dry roads with high friction (μ = 1) and on snowy roads with reduced friction (μ = 0.3). In addition, an AEB system adapted to road friction was designed for this study and compared with the conventional AEB on snowy roads with reduced friction. Ninety six drivers (48 males, 48 females) assigned to 5 age groups (20-29, 30-39, 40-49, 50-59 and 60-75 years) drove with AEB in the simulator. The drivers observed and evaluated the AEB's braking actions in response to an imminent rear-end collision at an intersection.

RESULTS: The results show that drivers' safety and trust in the conventional AEB were significantly lower on snowy roads, and the non-adaptive autonomous braking strategy was considered less appropriate on snowy as compared to dry roads. As expected, the adaptive AEB braking strategy was considered more appropriate for snowy roads than the non-adaptive strategy. In conditions of reduced friction drivers' subjective safety and trust were significantly improved when driving with the adaptive AEB as compared to the conventional AEB. Women felt less safe than men when AEB was braking. Differences between age groups were not of statistical significance.

CONCLUSIONS: Drivers notice the adaptation of the autonomous braking strategy on snowy roads with reduced friction. On snowy roads they feel safer and trust more the adaptive than the non-adaptive automation.

Language: en

Keywords

Autonomous emergency braking; adaptation to road friction; age; gender; safety; trust