Click here for a message "Concerns about quiet car legislation"
Quiet Cars and the Safety of Blind Pedestrians by Dona Sauerburger, M.A., COMS
The National Highway Traffic Safety Administration held a public meeting on quiet cars in Washington, DC June 23, 2008 to bring together government
policymakers, stakeholders from the
blind community, industry
representatives and public interest
groups to discuss the safety of blind
pedestrians encountering quiet cars
(including hybrids, all-electric vehicles
and quiet internal combustion engine
The following presentation was prepared in response to an invitation to speak at this meeting. Click here for the written paper that was submitted for the record.
I am very pleased to have the opportunity to participate in this discussion with NHTSA, as the topic of quiet cars is a very important one. I am an orientation and mobility specialist, and have been teaching people to cross streets for more than 38 years.
Traditionally, blind people use traffic sounds to determine EVERYTHING needed to cross streets, such as:
intersection geometry (width of the street, how many legs it has and at what angles, etc.);
traffic control and the appropriate time to cross (whether there is a signal and if so, what is the traffic pattern and when to cross, and if there is no signal or stop sign, when there is a gap in traffic long enough to cross);
alignment and position before crossing;
maintain alignment during crossing so that the person doesn't veer into speeding traffic in the street beside him;
avoid vehicles turning into their path.
In the 1940's, when our profession was developed, the sounds of the traffic were sufficient to accomplish all these tasks.
In 1969, when I started teaching people to cross streets, the traffic sounds were still sufficient - the average sound level for passenger cars at that time was about 90 dB.
However,* the U.S. Federal-Aid Highway Act of 1970 and the Noise Control Act of
directed the Federal Highway Administration and the Environmental
Protection Agency to develop standards for mitigating traffic
noise. The Noise Control Act of 1972 authorized the Environmental
Protection Agency to develop noise emission standards for motor and
engine powered equipment, including automobiles. To date, no federal
noise limits exist for cars, but currently in the U.S., automobile
manufacturers design cars to meet the European noise limit of 78 dBA or
less. (Federal Highway Administration, 1995,
Ken Feith, personal communication 2008).
Since the decibel system is logarithmic, this meant the sounds were reduced to less than half of what they had been.
Since that time, the sound of traffic has been diminishing at the same time that intersection geometry / traffic control have become increasingly complex and challenging.
Gradually, the sound of traffic has become in many situations insufficient for blind people to make all the determinations and judgments needed to cross streets safely.
Today, people can't always hear:
traffic at signalized intersections to determine geometry, alignment, timing, etc.
Sometimes this is because there is no traffic there to hear, sometimes it is because the sound of the traffic they need to hear is masked by the sound of other traffic that is idling or moving nearby.
approaching cars to determine gaps in traffic where there is no traffic control A study was done by Western Michigan University (Wall Emerson, R. and Sauerburger, D., in press) at quiet, two-lane residential streets. Blind people - some of whom are sitting in this room - listened for approaching vehicles. At some sites, even blind people with the keenest hearing could not hear all vehicles far enough away to be assured it was clear to cross when quiet. The sound level of the vehicles as they passed by was not highly correlated with how well the blind people could hear them - what was much more predictive was the level of ambient sound, and the geometry of the street (such as hills or bends in the road).
yielding vehicles In a study by the Federal Highway Administration (Inman, Davis and Sauerburger, 2005), blind subjects - again, some of whom are sitting in the room today - were able to hear yielding vehicles in both lanes at a two-lane roundabout an average of only 19% of the time. And of the instances when they thought they heard vehicles yielding in both lanes, they were wrong 14% of the time.
Therefore, the problem of "quiet cars" is really an extreme case of the general problem of diminishing sounds of traffic.
Our professional organization, the Orientation & Mobility Division of the Association for Education and Rehabilitation of the Blind and Visually Impaired, has been alarmed about the problem of quiet cars for many years.
In 1996 we passed a resolution urging that research be done to determine alternative technologies and strategies to accomplish street-crossing tasks in situations where there are insufficient vehicle sounds.
In 2000 we passed a resolution urging research with the specific goal of determining the minimum amount and nature of acoustic information necessary to accomplish the street-crossing tasks, and urging NHTSA to hold vehicle manufacturers accountable for meeting minimum acoustic information standards that are determined to be necessary to assure the life safety of pedestrians who are blind and visually impaired.
In 2004 we came back again, this time with a resolution that reflected a much broader perspective.
This resolution pointed out that...
. . . blind people aren't the only ones who use the sound of vehicles to navigate streets and parking lots safely.
Research by Tamara Bond and Randolph Easton at Boston College indicated that the sound of vehicles is used by all pedestrians. Their study was done at a two-lane street where students were asked to indicate when they felt it was safe to guide a young child across the street, and when it was no longer safe. A "risky decision" was one where the participant still felt it was safe to cross when, in fact, a car was too close (it would have reached them before their crossing was done).
The students in this study made "risky decisions" about 55% of the time, and when they were unable to see the vehicles and had to use hearing only, to no one's surprise they made risky decisions almost 80% of the time.
What was surprising is that when they could see the cars but were unable to hear them, they made about 10% more risky decisions than they did when they were able to hear the vehicles as well as see them. So apparently they need the sound of the cars to help them make safe judgments.
. . . the ability to hear vehicles is likely to decrease in view of efforts to reduce not just engine noise, but ALL sounds related to moving traffic.
In 1970 the U.S. Federal-Aid Highway Act mandated the Federal Highway Administration to develop noise standards for mitigating highway traffic noise (Federal Highway Administration, 1995).
So there are efforts to reduce the sound of moving vehicles, including the sound of tires and pavement.
For example, in 2001, Purdue's Institute for Safe, Quiet, and Durable Highways worked with the U.S. Department of Transportation to help tire manufactures design tires that make less noise (Wiebusch, 2001). In 2002 a $34 million Quiet Pavement Pilot Program was launched in Arizona to resurface highways with an asphalt rubber friction course overlay that can reduce the sound level of moving vehicles 6-12 dB(A) compared to concrete surfaces (Manuel, 2002).
This trend to quieter pavement and tires will make it even more difficult for pedestrians to hear the cars, increasing risky decisions and difficulties accomplishing safe street-crossing tasks for ALL pedestrians.
The 2004 AER resolution therefore urged that research be done to:
evaluate the effect of quiet vehicles on pedestrian safety, and
determine techniques for providing information that is equivalent to the acoustic cues that are currently provided by vehicle engines, which will enable blind pedestrians to cross streets;
evaluate the broader issues of the effect on the environmental access to street crossings and the wayfinding of blind pedestrians that are likely to occur if there are large numbers of quiet vehicles; and to
develop techniques and technologies to address whatever problems are found.
Finally, the resolution urged
NHTSA, FHWA, and the Access Board to promptly implement results of this research to provide acoustic safety and orientation information to all pedestrians
ALL pedestrians must be able to detect vehicles, because as research has shown, pedestrians who have the right of way are often ignored, even if they carry a white cane (Geruschat, D, and Hassan, S. 2005, Inman, Davis & Sauerburger, 2005)
They are also knocked down or run over. For example, I know of at least a half dozen people who have been bumped and/or knocked down by drivers who were looking to the left while turning right-on-red or turning right from a driveway into a busy street - the drivers each claimed that they never saw the pedestrian. And of course there is a well-recognized need for providing a sound for trucks that are backing up because of limited visibility, especially for children and people in wheelchairs.
And lest we think that being unable to detect cars moving in parking lots is not a serious matter, I will relate to you what happened to Maxine Deplane in a parking lot in the Maryland suburban community where I live. Maxine worked at my travel agency, and had normal vision and hearing and a warm smile whenever she greeted me. As she walked from her car to her grocery store, an elderly driver knocked Maxine down and then drove over her without realizing she was there. Maxine died a few hours later, after saying farewell to her husband who was summoned to the parking lot.
Therefore, all pedestrians must be able to detect vehicles! They cannot rely on drivers for their safety.
Houston, we have a problem, and it is urgent!
The problem is both broad, and complex.
Requiring a minimum noise for cars
may not be enough to address all the problems that are presented by insufficient traffic sounds, and
if it is not studied carefully, it may cause unintended consequences that make crossing even more difficult or dangerous. For example, at roundabouts and at congested signalized intersections, the sound of cars idling in the intersection may mask the sound of traffic that is necessary to hear in order to make safe street-crossing decisions.
Increasing the sound of cars is critical, but it is only one of a range of possible solutions for some of the problems caused by insufficient vehicle sound. We may also need solutions that provide alternative strategies for getting the information needed.
At signals, information about the walk phase can be provided with accessible pedestrian signals (APS).
At signals, the risk of turning cars that cannot be heard can be reduced with lead pedestrian intervals if the signal information is made accessible with APS.
Alignment information that is normally provided by traffic sounds may be provided with tactile strips and cues.
At roundabouts where the sound of approaching vehicles is masked by other vehicles, gap-in-traffic information to determine when it is clear to cross can be provided by installing traffic/pedestrian signals.
At streets with no traffic control, the risk of crossing and the need to hear vehicles approaching from a distance for gap-in-traffic information can be reduced by shortening the length of the crossing, and/or slowing the traffic, for example, with bulbouts and refuge islands.
However there are situations with no solution to substitute for the audible sound of the vehicle itself.
This is true not just for blind people, but for all pedestrians!
We therefore need research to:
determine the scope of problem(s) (in what situations does the insufficient or lack of sounds from vehicles cause a problem?);
develop effective solutions that don't create other problems for pedestrians;
determine what problems will be solved by simply enhancing the sound of cars (not with alternative design), and what kind of sound will address those problems adequately.
In other presentations at this meeting, we have heard about "quiet car" research being done in laboratories. Lab studies are important, of course, but it is also necessary to study real situations with real people.
Western Michigan University is conducting such research. An initial study verified suspicions that as hybrid vehicles go slower, they get quieter than other cars, although the difference is most noticeable only when they are going slower than about 15 mph.
But the importance of using blind people in these studies is illustrated by the fact that WMU found that when Toyota and Honda hybrid vehicles each approached subjects at 15-20 mph, even though the sound level of the Toyotas was measured as higher than that of the Honda, the Toyotas were much more difficult for the blind people to detect. They could hear the Hondas 5-6 seconds away but couldn't hear Toyotas going at the same speed until they were less than 2 seconds away.
So this is not a simple issue, solved by the level of sound alone. It may involve the frequency of sound or other features of sound, and we need to determine what those features might be.
WMU plans to do more research with hybrids and blind people at intersections with signals this August. The tasks needed to cross streets at signals are quite different from those needed to cross where there is no traffic control, and these need to be studied in real situations.
In conclusion, we urgently need comprehensive research to be done immediately ...
... on the effect of quiet cars on the street-crossing tasks and safety of all pedestrians;
... on the broader issue of street-crossing tasks, safety, and strategies used by blind people in a world where diminishing traffic sounds are mandated by government policy;
... to develop solutions and test their effectiveness.
* This is altered from the original presentation to correct the erroneous statement that "in 1972, the sound level of cars was reduced to no more than 78 dB." The U.S. has studied and considered sound restrictions but never established regulations regarding passenger vehicles.
Bond, T, and Easton, R. (in press). The relative contributions of audition and vision to pedestrian street crossing judgments. Journal of Visual Impairment and Blindness, AFB Press
Federal Highway Administration (1995). "Highway Traffic Noise Analysis and Abatement Policy and Guidance" FHWY Office of Environment and Planning, Noise and Air Quality Branch, Washington, DC
Wiener, W. R. (1997). Audition for the visually impaired traveler. In Welsh, R., Wiener, W. R., & Blasch B. B. (eds.) Foundations of Orientation and Mobility, Second Edition. AFB Press: New York, NY
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