Impact of adding artificially generated alert sound to hybrid electric vehicles on their detectability by pedestrians who are blind

Abstract

A repeated-measures design with block randomization was used for the study, in which 14 adults with visual impairments attempted to detect three different vehicles: a hybrid electric vehicle (HEV) with an artificially generated sound (Vehicle Sound for Pedestrians [VSP]), an HEV without the VSP, and a comparable internal combustion engine (ICE) vehicle. The VSP vehicle (mean +/− standard deviation [SD] = 38.3 +/− 14.8 m) was detected at a significantly farther distance than the HEV (mean +/− SD = 27.5 +/− 11.5 m), t = 4.823, p < 0.001, but no significant difference existed between the VSP and ICE vehicles (mean +/− SD = 34.5 +/− 14.3 m), t = 1.787, p = 0.10. Despite the overall sound level difference between the two test sites (parking lot = 48.7 dBA, roadway = 55.1 dBA), no significant difference in detection distance between the test sites was observed, F(1, 13) = 0.025, p = 0.88. No significant interaction was found between the vehicle type and test site, F(1.31, 16.98) = 0.272, p = 0.67. The findings of the study may help us understand how adding an artificially generated sound to an HEV could affect some of the orientation and mobility tasks performed by blind pedestrians.

Traffic Sounds and Cycling Safety: The Use of Electronic Devices by Cyclists and the Quietness of Hybrid and Electric Cars

“…Only one study (Hong, Cho & Ko, 2013) included a fully electric car -a low speed and light model. Kim et al (2012a) and Wiener et al (2006) used conventional and hybrid cars of the same make and model. Other studies do not provide details about the cars used.…”

“…At speeds above 30 km/h, and in some studies already above 15 -20 km/h, the sound level of two car types do not differ, most likely because of the tyre noise being dominant and not the engine noise. Kim et al (2012a) When driven at low speeds and in relatively quiet backgrounds, (hybrid) electric cars were more likely to remain undetected longer than conventional cars by both sighted and visually impaired pedestrians (see Table 1.3). The study of Hong, Cho & Ko (2013) found a difference between an electric and a hybrid car: the former was detected later when stationary or when driven at 30 km/h.…”

“…However, even conventional cars were not always detected at distances allowing safe crossing. Once the ambient sound level was above 45 -50 dB-A or when curves, hills and road-side trees obscured sounds, conventional cars were often detected too late to cross safely (box 1a) (Kim et al, 2012a;Wall Emerson et al, 2011;Wall Emerson & Sauerburger, 2008).…”

“…In the same study, the signal-to-noise ratio needed to distinguish between these paths was higher than the signal-to-noise ratio needed for vehicle detection. Kim et al (2012a) d Wall Emerson et al (2011 Hong, Cho & Ko (2013) f Mendonça et al(2013) g Kim et al (2012b) No studies into the detectability and localisation of (hybrid) electric cars performed with cyclists were found in the literature. Since hybrid cars emit less sound at low speeds, it can be expected that similar differences in detection as for pedestrians will apply for cyclists.…”

The Effectiveness of Straight Line Walk Application Used on Straight-Walking Skills for Blind Students

“…For example, vehicle sounds are used to determine the crossing location, up to a straight journey across the street (Barlow et al, 2005). The sound characteristics of the vehicle, as well as the surrounding environmental conditions, are estimated to affect detection of different environmental circumstances (Kim et al, 2012). This proves the focus of attention of research subjects in following the vehicle's voice to help them walk straight.…”