Proposed Highway Safety Rules for Hybrids Consider Needs of Guide Dog Users

Some incidents will explain why the Department of Transportation considers it important that hybrid and electric vehicles emit some level of sound that pedestrians, particularly those with vision impairments, can hear:

“I was on my way to work and got off the bus at the northwest corner of Jackson and Halsted. I made a left turn when I got off the bus, with Halsted on my left and Jackson in front me. When I went to cross Jackson my dog took me to the right as if there was an obstruction, but I didn't hear anything so I didn't know why he was going that way. I found out later that an SUV had pulled into the crosswalk to make a right on red. My dog had to go behind it because it jutted out into traffic. When we got across the street there was so much snow on the sidewalk that my dog had to take me around the right side of the car. It was only then that I realized it was a car that was blocking the intersection. The driver was about to turn right, and another pedestrian noticed that he hadn't seen me because he was looking the other way. The pedestrian shouted at him to hold still until I got out of the way. If that pedestrian hadn't noticed what was happening I would have been hit. I would have crossed the other street if I had heard the car there, but it was completely silent.”

Another visually impaired person describes being saved only because his dog pulled him back before stepping in front of a hybrid. One guide dog pushed its owner into a snowbank to save him.  In another incident, a guide dog user was hit and his leg broken when neither he nor his dog heard a car.  Yet another worried whether his dog should have heard a car since he had not:

“I had someone from Seeing Eye come down to reenact the incident and evaluate my dog. I wanted to make sure she was working well, that she really was looking. She did stop me just in time, but the driver had to jam on his brakes and when I reached out I could touch the car. The driver had swerved to avoid hitting me. I think not only blind people are in danger from these quiet cars, but so far blind people are the only ones trying to do anything about it. I think when there are more silent cars like all-electrics on the road I will totally lose my confidence.”

These comments were made by participants in a survey conducted by the National Federation for the Blind, specifically by the head of that organization’s Committee on Automobiles and Pedestrian Safety, Deborah Kent Stein. 

Proposed Highway Safety Rules

In proposing rules requiring that cars with quiet technology—electric cars and hybrids—emit at least some sound even when their engines are shut off, the National Highway Traffic Safety Administration (NHTSA) within the Department of Transportation indicates that a significant reason for such requirements concerns visually-impaired persons.  The risk from silent cars applies both to people who use guide dogs but also people who use the “structured discovery method of independent travel,” which involves using information provided by a white cane, traffic sounds, and other cues in order to travel safely. 

It should also be noted that being able to hear vehicles is sometimes important for guide and service dogs.  There are also individuals who suffer from both sight and hearing loss who depend on the dogs to guide them while recognizing dangerous sounds.   Also, some hearing or signal dogs, which work with individuals who have hearing impairments, are trained to recognize vehicle sounds so that they can alert their masters to oncoming cars while the two are walking.  These dogs will also benefit from the additional sound requirements. 

National Highway Traffic Safety Administration Analysis of the Needs of the Visually Impaired

The NHTSA notes that most guide dog schools require that individuals with whom dogs will be paired have some skill in using a white cane.  The guide dog does not generally lead the person, but primarily guides him or her around obstacles.  (Certain dogs, such as dogs in Israel and Australia that work with Alzheimer’s patients, do in fact lead their owners.)  For those who are visually impaired, traveling safely and independently involves substantial use of the sense of hearing. In its release proposing certain sound levels for hybrid and electric cars, the NHTSA elaborates:

“When traveling with a white cane or guide dog, the primary sound cue used by blind pedestrians is the sound of vehicle traffic, which serves two purposes: navigation and collision avoidance. Navigation involves not only ascertaining the proper time to enter a crosswalk and maintain a straight course through an intersection while crossing, but also the recognition of roadways and their traffic patterns and their relationship to sidewalks and other travel ways a blind or visually-impaired person might use.”

Collision avoidance is of tremendous concern to a blind person: 

“Sound emitted by individual vehicles, as opposed to the general sound of moving traffic, is critical. The sound of individual vehicles alerts blind travelers to the vehicle’s location, speed, and direction of travel. For example, a blind or visually-impaired person moving through a parking lot can hear and avoid vehicles entering or exiting the lot or looking for parking spaces; a blind person walking through a neighborhood can hear when a neighbor is backing out of a driveway. The vehicle sound also indicates to a blind or visually-impaired pedestrian whether a vehicle is making a turn, and if so, in which direction. The sound of individual vehicles also allows the blind traveler to detect and react to unusual or unexpected vehicle movement.”

The sound of a vehicle idling tells a visually-impaired person that the vehicle is not simply parked, and that it may move. At a driveway, the person will wait for the vehicle to pull out.  Even when they are not at intersections, visually-impaired persons listen to the sound of traffic constantly.  The sound of traffic passing helps them follow the roadway, inform them of roadway changes like curves, forks, or merges. 

“The sound of traffic is particularly important in negotiating intersections. By listening to the traffic, a blind or visually-impaired traveler can determine how the intersection is controlled (traffic signal, stop sign, etc.); how many lanes of traffic are involved; and any unusual characteristics of the intersection (e.g., three-way intersections or roundabouts). These determinations can be made by listening to the sounds of vehicle engines—often through one or two entire signal cycles—to determine driver behavior, which is usually a reliable indicator of the characteristics of the intersection. This includes the sound of stationary vehicles—particularly in multi-lane or oddly shaped intersections—because it is important to identify which lanes of traffic are active, when, and for how long; and to then follow the line of traffic that most nearly parallels the direction in which the traveler wishes to proceed. At the same time that the blind traveler is listening to the overall traffic pattern, he or she also listens for cues from individual vehicles, particularly when determining the precise moment to enter the crosswalk. At signaled intersections, an idling vehicle in the street parallel to the path of the traveler that accelerates and moves through the intersection is an indication that a traffic signal has just changed and that it is safe to proceed into the cross street, with maximum time to complete the crossing. In general, by crossing when the traffic flow is parallel to him or her, a blind individual can safely cross most intersections without difficulty. The individual will use the sound of the parallel traffic while crossing to maintain a roughly straight line through the intersection.”

Complex Intersection (NHTSA diagram)

Listening for cues requires taking in a great deal of information when the intersection is as complex as the one depicted in the diagram here.  A visually impaired-pedestrian will have to determine when vehicles are going straight, when left turns are occurring, and when stepping off the intermediate islands, will have to be aware that traffic on the fringes of the intersection may not be governed by lights, but only by stop or yield signs. 

As to hybrid vehicles (HVs) and electric vehicles (EVs), the NHTSA states:

“To the extent that there are more and more HVs and EVs on the road that are hard to detect, people who are blind or visually impaired will lose a key means—the sound of traffic—by which they determine when it is safe to cross streets, but also by which they orient themselves and navigate safely throughout their daily lives, avoiding dangers other than automobiles.”

Minimum Sound Requirements for Hybrid and Electric Vehicles

The proposed sound standards apply to electric vehicles and hybrids that are capable of propulsion in at least one forward gear, as well as in reverse, without the vehicle’s internal combustion engine (ICE) operating.  The Pedestrian Safety Enhancement Act (PSEA) of 2010 requires that hybrid and electric vehicles emit sound that pedestrians can hear in a range of ambient environments and contain acoustic signal content that pedestrians will recognize as being emitted from a vehicle. 

The proposed rules implementing the PSEA specify that a vehicle must, within half a second of activation of its starting system, emit a specific sound pressure level in each of eight octave bands.  Each octave band is identified by its center frequency. Sound frequency is measured in unit called Hertzes, universally abbreviated as “Hz.”  Human ears detect sound waves with frequencies ranging from 20 to 20,000, though vehicles need not emit sounds across this entire range.  The band center frequencies where vehicles must make sufficient sound to satisfy DOT’s proposal range from 315 to 5,000.  The decibel levels (technically, minimum sound pressure level (SPL) measured in decibels) required in the specified frequency ranges are from 31 to 60, depending on whether the vehicle is stationary, backing, or moving forward at 10 or 20 kilometers/hour.  This is expressed in a series in tables that will be used by engineers of vehicle manufacturers to assure that enough sound is being made either by the engine or by a separate sound system.  The tables in the proposal specify the following sound requirements:

	Minimum Sound Pressure Level (SPL), A-weighted decibels (dB)
1/3 octave band center frequency, HZ	Engine running, vehicle not moving	Vehicle backing up	Vehicle passing at 10 km/hour	Vehicle passing at 20 km/hour	Vehicle passing at 30 km/hour
315	42	45	48	54	59
400	43	46	49	55	59
500	43	46	49	56	60
2000	42	45	48	54	58
2500	39	42	45	51	56
3150	37	40	43	49	53
4000	34	36	39	46	50
5000	31	34	37	43	48

Notice that the greater the movement, the greater the sound requirement.  This is because of the increased risk and the higher level of ambient noise in moving traffic.  Currently, a 2010 Toyota Prius makes less than background noise when idling and stationary, an average of 44.2 dB when backing up, 53 dB when slowing from 20 to 10 mph, and 44.7 dB when passing at 6 mph (approximately 10 km/h). 

Conclusion

It is essential to consider the needs of individuals with disabilities when matters of safety arise and the Department of Transportation and the National Highway Traffic Safety Administration are to be commended for looking at the needs of those with visual impairments.  Because sound is the aspect of vehicle movement that presents dangers to pedestrian traffic, it is peculiar that this release made no mention of the hearing impaired.  The only mention of hearing loss in the release concerns that reduction of hearing that results because of ambient noise. It is noted that this kind of hearing loss tends to increase with age. 

The comment period on these proposed rules remains open until March 15, 2013.  The only automobile manufacturer to comment so far is Mercedes-Benz USA, which notes that one problem with the proposal is that drivers “stuck for extended periods of time in traffic congestion will be subject to constant sound emissions from their own vehicles, which they will be unable to turn off.”  It appears likely that some changes to the rules will be made before they are finalized.

Department of Transportation: National Highway Traffic Safety Administration, Federal Motor Vehicle Safety Standards; Minimum Sound Requirements for Hybrid and Electric Vehicles, 78 Fed. Reg. 2798 (January 14, 2013)

This blog will be periodically updated to discuss significant comments from other manufacturers and guide or service dog organizations. Thanks to Dennis Civiello, Clare McLaughlin, and Ronald Keats for comments and corrections.  

Additional Note.  The January 2013 issue of Car and Driver (p. 65) contains a description of a Department of Transportation study concerning a wireless car-to-car connectivity to avoid collisions. The piece indicates that this Wi-Fi technology could be mandatory in American cars by 2020.  Car and Driver states:

"Taking the idea further, GM wants to help drivers avoid mowing down pedestrians. The underlying technology, called Wi-Fi Direct, allows a smartphone in a car to communicate with a phone carried by a pedestrian without routing the dialogue through cell phone towers.  The direct connection cuts the time requited to identify a risk from eight seconds to one."

The NHTSA should consider the degree this type of technology might obviate the need for additional sounds in vehicles.  General Motors has not commented on the proposed regulations as of this writing (January 28, 2012).