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Hybrid cars, too quiet to be free from blind spot

6, 25. 2007

   Hybrid cars are gaining popularity because they are friendly to Earth. As they run by both gasoline engine and electric motor, they give good mileage. Their other characteristic is that they are so quiet, and this is causing an unexpected problem. Some consumers have complained that they are often scared because such cars get so close behind them without their knowing. The Land, Infrastructure and Transport Ministry is working out measures, but it seems to need some more time before it can come up with a acceptable solution.

Outlandish idea of horn with sound pleasant to ear

Pleasant sound for hybrid car horn asked
Pleasant sound for hybrid car horn asked

   The ministry issued a report in the summer of 2006 on "safety measure for future cars aimed at reducing traffic accidents" in which it pointed out that "pedestrians are often slow in noticing the approaching of electric automobiles, including hybrid cars, because of their quietness". It thus recommended study the matter. Carmakers also say that they have received inquiries from the drivers of hybrid cars if it would be possible to equip their vehicles with horns that would make pleasant sound to notify pedestrians when they them. The drives said the people on the street can not hear the approach of hybrid cars well because they are so quiet, and the drivers would hesitate to startle them with the lout honking, according to the carmakers.

   Responding to the ministry's report, the Japan Automobile Manufacturers Association, established jointly by the government and automakers, are beginning to look into the matter. Study has to be conducted at first to check if pedestrians are really slow in noticing the approach of hybrid cars. So far, statistics do not show that a larger number of pedestrians tend to be hit by hybrid cars than by non-hybrid cars. It was found, however, that an increased number of pedestrians could not hear hybrid cars approaching them from behind at speeds less than 15 kilometers an hour.

   Even at a speed of that of a bicycle, it has to be taken into consideration that a car weighs more than a ton. The association took a note that a pedestrian hit by a car at this speed would very likely fall down and with the head severely hitting the ground, and started to work out measures.

   The work, however, is facing unexpected difficulty. Regarding the "horn with a pleasant sound", the tone and volume of the car horn are regulated by the safety standard under the law concerning the road transportation vehicles. Moreover, any sounding device that is not distinguishable from the car horn is banned under the same safety regulation. This problem seems to be solved easily by amending the law. But a carmaker pointed out that a horn with a pleasant sound might not be a perfect solution as the horn has to be operated by the driver, meaning that the safety of the pedestrian is made dependent on the driver.

The ministry putting off specific measure until some other time

   The association has come up with another idea. Called "car approaching warning device", it suggested to notify the pedestrian of the approach of a car by an amplified sound coming out of the car's engine room. A drawback of this, however, is that it might cause a noise pollution especially in residential areas at night. The association constructed model houses along a driving test course to simulate residential district to test more than 10 different tones of sounds, including those of the train station bell, automobile engines and chimes. But a decisive conclusion could not be achieved. Another problem that came up was that, supposing an acceptable sound could be found, the pedestrians would not know that the sound is a warning that car is approaching unless the public is sufficiently educated before hand, the association pointed out.

   The trial for the use of the warning device which the association claims to be "unprecedented in the world" has been terminated for the time being, and the ministry is putting off working out of a specific measure until some other time. The batteries and motors used by hybrid cars are certain to be improve almost every day from now on. The same problem may have to be dealt with again in the future.

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