At about 4 p.m. yesterday, a caravan of ten "pedal cars" left Harvard Square and rolled amidst the traffic of Mt. Auburn St. towards Putnam Square.

Barbara Ackermann, Mayor of Cambridge, and Alan Altshuler, Cambridge Secretary of Transportation, led the motorcade--or rather pedalcade--to demonstrate the pedal car as a non-polluting method of transportation.

The $379 pedal car, or PPV (for people-powered vehicle), is a three wheeled adult version of the toy pedal-powered fire truck common to children. It is six and one-half feet long, comes equipped with a three-speed transmission and has two adjustable bucket seats.

"The pedal car is really useful around Cambridge," Ansti Benfield, chief promoter for the demonstration, said yesterday.

Benfield first heard of the pedal car from a magazine in November. By December she owned the first pedal car in New England, according to David H. Leigh, marketing director of People Peddlers Inc., the New England distributor of the pedal car.

Benfield estimates that within six months there will be about 600 pedal cars in Cambridge.

"We're here to convince the traffic and parking people that it's safe to put them on the road," she said.

The pedal car is easy to ride, Benfield said, but "it would be nice if it had two lower gears for the hills."

The pedal car has a speed of about 15 to 20 miles per hour on a straightaway Benfield said. Leigh, however, said that he had clocked it as fast as 35 miles per hour.

What about the ride?

"Very non-polluting," Ackermann said after pedalling a block.

"Not too good for the nerves," Altshuler commented as he looked at the traffic, "but good for the lungs."