On the streets of San Francisco, the buses are beeping again. Beeping for safety.

The San Francisco Municipal Transportation Agency Board of Directors reversed an earlier policy that had Muni buses turning off the noisemaker that sounds when the bus is preparing to make a right turn. The beep-beep-beep is back to let pedestrians, bike riders and motor vehicles know of the potential danger.

The beepers were disabled several years back because of complaints from residential neighborhoods about the noise late at night or early in the morning.

It amounted to a decision of safety vs. annoyance and, said board of directors Chairman Tom Nolan, “I come down on the side of safety every time.” Nolan himself is a regular Muni rider.

Muni, with its historic cable cars charming tourists while getting commuters to work up and over San Francisco’s famed hills, bills itself as the most diverse transit agency in the world. The cable cars colleagues include electric trolley coaches, light rail vehicles, diesel buses and alternative fuel vehicles. It all adds up to about 200 million riders annually.

The San Francisco Municipal Transportation Agency has a 2008-09 budget of $784.1 million. Its revenues come from parking and traffic fees and fines, transit fares, grants, advertising and interest payments.

At a meeting in February, Ken McDonald, Muni’s chief operating officer, referred to a staff review that suggested two recent Muni accidents involving collisions between right-turning buses and pedestrians, might have been prevented by activated beepers.

Muni vehicles reported 47 injury collisions with pedestrians in 2006, increasing to 59 in 2007. The figures for Muni vehicle-bicycle injury collisions was 16 in 2006, declining to 12 in 2007.

The beepers are intended to issue warnings at 65 to 75 decibels when an individual is 30 feet from the bus, and 75 to 85 decibels from five feet away. The lower end of that range is pegged as a normal conversational level. Nolan said the sound is about the same volume as the tone that sounds when a bus “kneels” for those who need a flat surface to board the bus.