Earlier this morning, we wrote about GM's announcement that engineers developing the 2011 Chevrolet Volt have partnered with the National Federation of the Blind to figure out "a safe level of sound" from the company's first extended-range electric vehicle.

Our subsequent interview with Tony Posawatz, vehicle line director for the 2011 Volt extended-range electric car, helped us understand some details of the Volt's Pedestrian-Friendly Alert System that we hadn't known.

Drivers to sound the alert

For one thing, the system will be driver actuated, rather than automatically producing sound at neighborhood speeds. Drivers will trigger it just like the "flash-to-pass" function now built into many turn-signal/light-switch combination levers.

The goal, Posawatz said, was to produce an "automotive quality sound" that pedestrians would instantly recognize, without confusing it for the horn. He described it as "a series of low horn audio signals or cues," but said the precise sound is "still being fine-tuned."

Lights as well as sound

At speeds under 35 miles per hour, the system not only emits that characteristic sound, but also flashes the Volt's lights. Though flashing lights may not be useful to vision-impaired pedestrians, they add an additional layer of warning for children, runners, cyclists, and others who may be unaware that a two-ton vehicle is driving silently toward them.

The alert sound is distinctive enough, Posawatz said, that it may become a way for Volt drivers to acknowledge each other, just as Corvette drivers and Harley-Davidson riders signal each other as they pass.

Hybrids hit pedestrians more

The imminent arrival of all-electric cars like the 2011 Chevrolet Volt and the 2012 Nissan Leaf has raised the level of concern among advocates for the blind about the lack of noise from hybrids running in electric mode.

Recent preliminary data from a National Highway Traffic Safety Administration (NHTSA) study appears to show that hybrids hit pedestrians more often than non-hybrid vehicles. With statistical information now demonstrating that risk, carmakers are lining up to work with groups like the NFB.

1911 Daimler Touring car king size horn

1911 Daimler Touring car king size horn