Tokyo ? Toyota Motor Corp. and Fujitsu Ten Ltd., a major manufacturer of automobile accessories, will jointly develop an automatic warning system for hybrid and electric vehicles to warn pedestrians of their approach, sources have said.

Electric vehicles and some hybrid cars are very quiet when driven at low speeds and could endanger pedestrians who might not hear them approaching. Other automakers are likely to follow suit in devising measures to address the problem.

The two companies are planning to conduct a related experiment soon on single-seat electric vehicles used in the lobby of Chubu Airport in Tokoname, Aichi Prefecture. The experiment will test various sounds to warn pedestrians that a vehicle is approaching, to find “the right tune at the right volume so people are alerted but don’t find the sound annoying,” an official close to the development team said.

The two companies also will study the development of a system that, by synchronizing with obstacle-detection radar, would change the alarm’s tune and volume in accordance with such factors as the vehicle’s distance from pedestrians, crowd density and surrounding noise.

The companies will collect the necessary data by July 2010 and expedite their efforts to commercialize the product.