John K Pollard

Humans and Intelligent Vehicles: The Hope, the Help, and the Harm

Intelligent vehicles offer hope for a world in which crashes are rare, congestion is reduced, carbon emissions are decreased, and mobility is extended to a wider population. As long as humans are in the loop, over a half century of research in human factors suggests that this hope is unlikely to become a reality unless careful attention is paid to human behavior and, conversely, the potential for harm is real if little attention is given to said behavior. Different challenges lie with each of the two middle levels of automation which are the primary focus of this article. With Level 2 automation (National Highway Traffic Safety Administration; NHTSA), the driver is removed from always having to control the position and speed of the vehicle, but is still required to monitor both position and speed. Humans are notoriously bad at vigilance tasks, and can quickly lose situation awareness. Moreover, even if vigilant, the driver needs to interact with the vehicle. But voice-activated systems which let the driver continue to glance at the forward roadway are proving to be a potential source of cognitive distraction. With Level 3 automation (NHTSA), the driver is out of the loop most of the time, but will still need to interact with the vehicle. Critical skills can be lost over time. Unexpected transfers of control need to be considered. The surface transportation and aviation human factors communities have proposed ways to solve the problems that will inevitably arise, either through careful experimentation or extensions of existing research.

Auditory Detectability of Hybrid Electric Vehicles by Blind Pedestrians

Hybrid electric vehicles (HEVs) in low-speed operation may introduce a safety issue for pedestrians. This study compares the auditory detectability of HEVs and internal combustion engine vehicles among pedestrians who are legally blind. Independent travelers, with self-reported normal hearing, listened to binaural audio recordings of two HEVs and two internal combustion engine vehicles in three operating conditions and two different ambient sound levels. The operating conditions include approaching at a constant speed (6 mph), backing out at 5 mph, and slowing from 20 to 10 mph (as if to turn right). The ambient sound levels simulated a quiet rural [31.2 dB(A)] environment and a moderately noisy suburban [49.8 dB(A)] environment. Overall, participants took longer to detect HEVs (operated in electric mode). Vehicle type, ambient level, and operating condition had a significant effect on response time. Candidate countermeasures are discussed in terms of types of information provided (direction, rate of speed change), useful range of detection of vehicles by pedestrians, warning time, acceptability, and barriers to implementation.

Evaluation of sounds for hybrid and electric vehicles operating at low speed

Electric vehicles (EV) and hybrid electric vehicles (HEVs), operated at low speeds may reduce auditory cues used by pedestrians to assess the state of nearby traffic creating a safety issue. This field study compares the auditory detectability of numerous synthetic sounds for hybrid and electric vehicles operating at a low speed. The sample includes pedestrians who are sighted and legally blind, independent travelers, with self-reported normal hearing. The test site has the acoustic characteristic of an urban area with a typical ambient noise level of approximately 58-61 dB (A). Dependent variables include proportion of detection and detection distance. Synthetic sounds tested, that resemble those of an internal combustion engine (ICE) vehicle, produce similar detection distances as the actual ICE vehicle tested for a 6 mph constant speed operation. In some instances, synthetic sounds designed according to psychoacoustic principles were detected much sooner than the reference ICE vehicle tested. Synthetic sounds that contain only the fundamental component of combustion noise, but lack the harmonics and other high-frequency characteristics of an actual ICE were relatively ineffective, with their detection distances being only about half of those of an ICE vehicle.

Acoustic Characteristics of Hybrid Electric Vehicles and Safety of Blind Pedestrians

Quieter cars, such as electric vehicles and hybrid electric vehicles (HEVs), may reduce auditory cues used by pedestrians to assess the state of nearby traffic and, as a result, their use may have an adverse impact on pedestrian safety. To document differences in the sound levels of HEVs and internal combustion engine (ICE) vehicles, the authors measured the sound pressure levels in one-third octave bands of three HEVs and three corresponding ICE vehicles for the following operating conditions: idle, backing up at 5 mph, approaching at a constant speed (6, 10, 20, 30, and 40 mph), accelerating from stop, and slowing from 20 to 10 mph at 3.28 ft/s2. Sound level results comparing the HEVs with the ICE vehicles are presented. In general, HEVs have lower sound levels than ICE vehicles for operating conditions below 20 mph; but above 20 mph, the sound from road–tire interactions dominates and the sound levels of the two vehicle types converge.