Major Failure Events of Automated Highway Systems: Three Scenarios from the Driver’s Perspective

Automated Highway Systems (AHS) have the potential for offering large capacity and safety gains without requiring significant amounts of additional right-of-way. Since the general public will be the users of the AHS, human factors must play a pivotal role in the research and development of AVCS technologies and AHS operation. In two companion reports, three attributes critical to AHS human factors were identified and seven scenarios featuring variations in these attributes proposed. To ensure the identification of all major compounding attribute combinations, detailed operational events, from the perspective of the driver, were identified. This paper focuses on failure events, where a failure event is defined to be the occurrence of a functional failure during a normal operational event. After briefly reviewing the seven "first-generation'' scenarios, this report first describes the criteria for selecting the three "second-generation'' scenarios and then reports the selection result. While examining each of the normal operational events identified for the three scenarios, we identify possibly multiple major failure events by assuming the failure of one operational function at a time. Failure events resulting from the failure of multiple operational functions can be inferred. For each failure event, we also define possible failure consequences and possible system responses to resolve the failure event. These second-generation scenarios are selected for studying AHS human factors and are not being advocated by the authors as the better deployment choices among the seven first-generation scenarios, even from the human-factors point-of-view. Similarly, the responses provided for the major failure events are not being advocated as the better ones. Rather, to truly identify human capability in failure/emergency situations and not to rule out possible human abilities prematurely, we tend to stretchthe limit of human capability in the responses. The true human capability is a crucial subject for future investigation.