Objective: We investigated driver acceptance of alerts to pedestrian alerts issued by a night vision active safety system with pedestrian detection functionality using a method that leverages scarce and expensive field operational test data.

Background: Driver acceptance of automotive active safety systems is a key factor to promote system use and implies a need for a method to assess factors influencing driver acceptance.

Method: In a field operational test, ten drivers drove instrumented vehicles equipped with a preproduction night vision system with pedestrian detection software. In a follow-up experiment, the 10 drivers and 25 additional volunteers without experience with the system watched 57 clips with pedestrian encounters gathered during the field operational test. They rated the acceptance of an alert to each pedestrian encounter.

Results: Levels of rating concordance were significant between drivers who experienced the encounters and participants who did not. Two contextual variables, pedestrian location and motion, were found to influence ratings.

Conclusion: The subjective acceptance rating method provides consistent measures of acceptance in a controlled environment and makes it possible to leverage expensive field operational test data within the confines of the laboratory.

Application: The study identifies sources of contextual sensitivity to alerts issued by an active safety system and demonstrates the utility of using subjective driver acceptance criteria to inform active safety system design.

In this paper I address the issue of false alarms as they relate to the development of automotive active safety systems. I argue that false alarms are not only unavoidable; they should be considered an integral part of the design of active safety systems that address potential accident situations. Accidents are rare. Hence the base rate of true alerts will also be rare. This fact has two undesirable consequences if designers strive to eliminate all false alarms. First, the few true alerts would be so rare that the driver’s reaction can not be expected to be efficient. Second, the few issued alerts would be insufficient in number to enable drivers to calibrate trust in the system. I suggest that it is more prudent to acknowledge that there will be false alarms and focus on achieving driver acceptance for the issued alerts. We can take advantage of the drivers’ subjective perception of potential accident situations to guide the specification of the system’s alerting criteria. Such systems are likely to achieve higher driver acceptance.

This thesis develops and tests an empirical method to quantifying drivers’ level of acceptance for alerts issued by automotive active safety systems. The method uses drivers’ subjective level of acceptance for alerts that are literally false alarms as a measure to guide the development of alerting criteria that can be used by active safety systems. Design for driver acceptance aims at developing systems that overcome drivers’ dislike for false alarms by issuing alerts only when drivers finds them reasonable and therefore are likely to accept them. The method attempts to bridge the gap between field experiments with a high level of ecological validity and lab based experiments with a high level of experimental control. By presenting subjects with video recordings of field data (e.g., traffic incidents and other situations of interest), the method retains high levels of both experimental control and ecological validity.

This thesis first develops the theoretical arguments for the view that false alarms are not only unavoidable, but also that some false alarms are actually useful and, hence, desirable as they provide useful information that can be used (by the proposed method) to assess driver acceptance of active safety systems. The second part of this thesis consists of a  series of empirical studies that demonstrates the application of the assessment method. The three empirical studies showed that drivers’ subjective level of acceptance for alerts that are literally false alarms are a useful measure that can guide system designers in defining activation criteria for active safety systems. The method used to collect the driver’s subjective acceptance levels has also been shown to produce reliable and reproducible data that align with the view of the drivers who experienced the situations in the field. By eliciting responses from a large number of observers, we leverage the high cost of field data and generate sample sizes that are amenable to statistical tests of significance.

Objective: We investigated driver acceptance of alerts to left-turn encroachment incidents that do not produce a crash. If an event that produces a crash is the criterion for a "true" alert, all the alerts we studied are technically false alarms. Our aim was to inform the design of intersection-assist active safety systems. Background: The premise of this study is that it may be possible to overcome driver resistance to alerts that are false alarms by designing systems to issue alerts when and only when drivers would expect and accept them. Method: Participants were passengers in a driving simulator that presented left-turn encroachment incidents. Participant point of view, the direction of encroachment, and postencroachment time (PET) were manipulated to produce 36 near-crash incidents. After viewing each incident, the participant rated the relative acceptability of a hypothetical alert to it. Results: Repeated-measures ANOVA and logistic regression indicate that acceptability varies inversely with PET. At PET intervals less than 2.2 s, driver point of view and encroachment direction interact. At PET intervals more than 2.2 s, alerts to lateral encroachments are more acceptable than alerts to oncoming encroachments. Conclusion: Driver acceptance of alerts by active safety systems will be sensitive to context. Application: This study demonstrates the utility of eliciting subjective criteria to inform system design to match driver (user) expectations. Intersection-assist active safety systems will need to be designed to adapt to the interaction of driver point of view, the direction of encroachment, and PET.

The purpose of this paper is to document the utility of a novel empirical approach to quantifying the relative level with which drivers are likely to welcome an alert from an active safety system. We discuss an experiment that applies this approach and show how the level of acceptance varies across traffic situations and driver point of view. The results reveal that both point-of-view and encroachment direction should be considered when designing active safety systems that would alert drivers to impending encroachment incidents.

The objective of this project is to develop and test a multi-method empirical approach for predicting drivers- assessments of the level of acceptability of a warning issued in response to accidents, near-accidents, and other incidents. The role of humans (drivers) in the pre-crash phase means that systems that protect occupants and pedestrians must be seen as distributed, cognitive systems. Driver acceptance therefore has to be an important design goal. One obstacle to acceptance is the human dislike for false alarms. An approach to overcoming driver dislike for false alarms is to focus on driver expectations and to design systems to issue alarms when and only when the driver is likely to accept them. In this paper we discuss one such approach.