[nfbwatlk] Fw: How an electric car could kill you

[Albert Sanchez]

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From: LPovinelli at aol.com 
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Subject: How an electric car could kill you


From: "John Rae " rae at blindcanadians.ca
Sent: Tuesday, June 30, 2009 10:27 AM
Subject: How an electric car could kill you


UNINTENDED CONSEQUENCES
How an electric car could kill you

Toronto Star, May 31, 2009

When cars run on electric power, they not only save fuel and cut emissions but also operate more quietly. Ordinarily, people might welcome quieter cars on the roads. However, as the use of hybrid and electric vehicles grows, a new concern is growing too: Pedestrians and cyclists find it hard to hear them coming, especially when the cars are moving slowly through a busy town or manoeuvring in a parking lot.

Some drivers say that when their cars are in electric mode people are more likely to step out in front of them. The solution, many now believe, is to fit electric and hybrid cars with external sound systems.

A bill going through the U.S. Congress wants to establish a minimum level of sound for vehicles that are not using an internal-combustion engine, so that blind people and other pedestrians can hear them coming.

The bill's proponents also want that audible alert to be one that will help people judge the direction and speed of the vehicle. A similar idea is being explored by the European Commission.

Although there is little data on accidents, the latest research suggests there is cause for concern. Vehicles operating in electric mode can be particularly hard to hear below about 30 km/h, according to experiments by Lawrence Rosenblum and his colleagues at the University of California, Riverside. Above that speed, the sound of the tires and of air flowing over the vehicle starts to make it more audible.

The researchers made sophisticated recordings of Toyota Prius hybrids
running on electric power and gasoline-engined cars approaching at eight
km/h from different directions. These were played to a group of subjects
wearing headphones. The subjects were asked to press one of two buttons to
identify which way the vehicle was coming from as quickly and accurately 
as possible.

As expected, they could determine the direction of the gasoline-engined 
cars much faster. When natural background sounds, like the engine tick-over of 
a parked car, were added, the hybrids' direction sometimes could not be
detected until they were perilously close. Both sighted and blind subjects
gave similar results.

What sort of noise should electric-powered cars make? Beep, as some
pedestrian crossings do? Buzz like a power tool?

Having worked with blind subjects, Rosenblum is convinced of a different
answer: "People want cars to sound like cars."

That sound need not be very loud. Just slightly enhancing the noise of an
oncoming electric vehicle, he says, would be enough to engage the auditory
mechanisms that the brain uses to locate approaching sounds.

Systems to do this are already being developed. Lotus Engineering, the
consultancy of a British sports-carmaker, recently signed an agreement 
with Harman Becker, a producer of audio systems, to commercialize one.

Lotus has worked on a number of hybrid and electric vehicles, and it was
while these were moving around its factory that the engineers thought they
would be safer if they made a noise.

The system Lotus uses was originally developed for a different reason: to
cancel out intrusive noises inside a car. Sound-cancelling works by
analyzing any unwanted frequencies and then producing counteracting ones.

The Lotus system was adapted so that it could also produce sounds that
change with speed and use of the throttle, providing a familiar audible
"feedback" to drivers of vehicles with a silent engine. Adding external
speakers allows pedestrians to hear the noise, too.

It is possible to create a different sound within a car from the one that 
is heard outside, says Colin Peachey, a chief engineer with Lotus.
Manufacturers could create their own sounds according to how they perceive
their models.

Carmakers already take engine noises seriously enough to use acoustic
engineers to tune exhaust pipes, especially for high-performance cars.
Drivers of electric cars might even be able to select different engine
sounds, and maybe download them like ringtones.

Although some drivers might want to cruise in an electric car thundering 
to the sound of a mighty V8 engine, it is not necessary - and traffic police
may have something to say about it. Synthesized engine noises could even
help reduce noise pollution, says Peachey.

For instance, sound from the speakers at the front of an electric car (or
the rear if reversing) is highly directional. This means it is more likely
to be noticed by pedestrians in front of or behind the vehicle. The noise
from an internal-combustion engine, however, radiates in many directions -
including upward into offices and bedrooms.

Unique engine noises would still be possible. A sound generator will be
fitted to the Fisker Karma, a luxury plug-in electric hybrid that goes 
into production later this year. It will both alert pedestrians and, says
Fisker's Russell Datz, enhance the "driver experience."

The Economist


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