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Hybrid Cars: Too Quiet to Be Safe?

Going green? Considering one of the new hybrids those cars that run on gasoline and electric battery. A lot of consumers are looking at these alternatives to $4.59 a gallon gas and rising. It costs $150 to fill an SUV. Some of us bought our first cars for $150 (58 Beetle with a bad clutch, anybody?).

Check out the growing popularity of hybrids in the face of growing gas prices:

  • In 2008, Toyota will sell 280,000 hybrids alone. The Prius is the most popular model.
  • Honda hybrid light duty vehicles increased by 4% and are growing FAST.
  • All U.S. manufacturers will have a selection of hybrids to market by 2011.
  • The number of hybrids on the road is expected to double in the next 12 months.
  • Analysts are predicting gas at $5.00 a gallon by the end of the year in many areas, further driving the demand for hybrid cars.

All good, right? All green? Well, the green part is right. These hybrids do use less gasoline but, as with most new technology, hybrid cars bring more than good gas mileage. They also bring a potential problem, especially for persons with hearing loss and vision loss.

Sometimes Things Are Too Quiet

A little background is in order: hybrid cars use both a small, fuel-efficient gas-driven engine and an electric engine powered by a battery. Have you ever driven in one of these vehicles? It takes some getting used to.

Toyota Prius

You see, the hybrid switches from gas power to electric power automatically as power demands change, i.e. you step on the gas. So, when youre trying to enter the Slawson Cutoff at 60 mph, the gasoline engine gives the car a boost. And you can hear that gasoline engine just as in any other gas-powered vehicle.

The problem comes when the car switches to all-electric mode. The effect is eerie the first time you experience it. The car suddenly goes silent, powered only by the electric motor and stored energy from the battery. You get used to it quickly, but when you first drive one of these green-age cars, some adjustment is necessary and were not talking about the rearview mirror. When it sounds like your car has shut down completely, its a little spooky.

Low-Hearing, Low-Vision, Children and You: At Risk?

Thats a fact. Silent cars can present risk to all of us.

Scene: You park your car at the mall and walk to the entrance. A hybrid, idling using its electric motor, doesnt make a sound. Suddenly, as you pass the silent hybrid, the driver pulls out, not seeing you. The results could be serious. Very serious.


Parking lots and hybrids pose safety concern for those with hearing loss.

Were all at higher risk when we cant hear vehicles. Our brains have become hard-wired to recognize the sound of a car engine and the sound the cars four tires make against asphalt. These are sounds we recognize without thinking because weve heard them for so long.

The problem is more complicated for low-vision, low-hearing and children pedestrians. Low-vision pedestrians rely on the sounds cars make to determine a cars location or when its safe to cross a road, for example. Individuals with mild to moderate hearing loss can still hear a car rumble to life; however would have difficulty hearing a hybrid car running on the electric mode. If theyre close enough to the vehicle, they can feel the cars vibration.

So, individuals with sight or hearing loss face a special problem with the quietness of hybrid cars. And so do children. Kids are often more engaged in their activities than street traffic but even children recognize the sound of an approaching car. Not so when a hybrid is running on electric power.

Yes, it does sound like one of those you cant win situations, but fortunately the auto industry and the federal government have taken steps to remedy this potentially dangerous problem.

Beep! Beep! Beep!?

Oh no, are we going to have a fleet of cars beeping and chirping to be heard as they drive along quiet country roads in electric mode?

An article, titled Subtle Changes Can Make Hybrids Safely Heard, found in the Tennessean and written by an advisor to the Society of Automobile Engineers, clarifies House Bill 5734, The Pedestrian Safety Enhancement Act of 2008 which directs the Secretary of Transportation to conduct a two-year study on how to best solve the problem of silent vehicles so were all a little safer walking the streets, with a special emphasis on our neighbors with special needs.

The bill also requires hybrid manufacturers to have solutions in place by 2010. Now, it usually takes a year or two of testing to implement a new system to solve a problem so car makers are well on their way to finding solutions.

So, are hybrids going to be the battery-powered noise-makers on our roads? Not according to the Society of Automobile Engineers. Phew! How many of us could live with the constant beeping of every hybrid that drives by?

According to the articles author, and SAE spokesperson, Lawrence Rosenblum, the changes will be much more subtle, providing the sound cues we all need to identify the location, speed and direction of cars. According to Rosenblum, First, hybrids and EVs are functionally silent only when traveling in electric mode, below 20 mph. Faster than that, and all cars produce enough tire noise to be audible from a safe distance. Of course, it is at slow speeds that cars are closest to pedestrians, whether in parking lots or backing out of driveways, and the greatest danger exists. But it is only at these slow speeds that some change is necessary.

Rosenbaum continues his explanation. Secondly, only a subtle enhancement of sound will be needed. Hybrids won't beep, chirp or produce an alarm. Beeps and chirps are more distracting than they are perceptually useful. The enhancing sound probably will be the simulated sounds of a very quiet engine (think cooling fan), or of rolling tires. For purposes of auditory utility and simple familiarity, the safest sounds are car sounds. These sounds will be barely noticeable to most of us. Not much sound is needed for the auditory system to warn us about hazards, as long as it's the right sound.

The key is brain sensitivity that we use to keep us safe. This sensitivity identifies potential approaching dangers such as cars backing out even as were thinking about something else entirely. The auditory (hearing) system basically runs on auto-pilot. So, if we hear recognizable car sounds were more apt to act instinctively to avoid potential danger.

So what can we expect to hear from hybrids in the next couple of years? The gentle whirr and the sound of rubber meeting the road. Just enough noise to warn us of an approaching vehicle but not so much as to drive us all crazy.

Safe, sensible and green. Now thats a combination you cant beat.

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