Cycling Reaches ‘Critical Mass’ : Transportation: Bike riders revel in their monthly group protest against cars in San Francisco. But angry rush-hour drivers blare horns and shout curses.

It is half past 5 on the final Friday evening of June, and hundreds of people have gathered in the heart of the financial district, filling a public plaza beside San Francisco Bay. Some wear suits and ties. Others sport Day-Glo spandex. All share one thing in common--a bicycle.

Young and old, fit and flabby, they have come together for “Critical Mass,” an extraordinary monthly happening that clogs San Francisco’s busiest downtown streets with bikes during rush hour.

At the stroke of 6, the ting-a-ling of bicycle bells rings out. Then, with loud whoops and whistles, the riders set forth, oozing onto Market Street as a phalanx of motorcycle cops block traffic and clear their way.

“Long live pedal power!” shouts one cyclist astride a battered, fat-tired beach cruiser. “Death to cars!” cries another aboard a more upscale Italian two-wheeler.

Stretching five or six city blocks in length, the colorful caravan has the giddy feel of a parade. There are cyclists in top hats and tails, cyclists towing toddlers in wagons and cyclists wearing gas masks in a silent statement against air pollution.

But Critical Mass is more than a two-wheeled party. It is, in essence, a moving sit-in--a friendly seizure of space by those who believe cars should not always rule the road.

“The typical urban experience on a bike is that you are alone, cars are exhausting on you and drivers are honking and threatening you and basically treating you like scum,” said Chris Carlsson, who owns a typesetting business and never misses a ride. “That’s why Critical Mass is so euphoric. You don’t have those worries, and bicycling becomes a social experience.”

Pioneered in San Francisco, the Critical Mass concept has quickly spread beyond the Bay Area, prompting duplicates in Manhattan; Austin, Tex.; Eugene, Ore., and other cities. Rio de Janeiro has a weekly ride that draws 5,000 cyclists. And next month, the ritual will invade Southern California with a ride in Huntington Beach.

Participants call the excursions an innocuous celebration of cycling, and tourists and downtown pedestrians seem charmed by the festive affairs.

But car-bound commuters delayed by the cyclists often take a different view. In a recent letter to the San Francisco Chronicle, one critic declared himself “sick and tired” of being inconvenienced. The bikers, he said, are “ignorant, backward-headed thrill-seekers” who belong in jail.

The city’s Parking and Traffic Commission agrees. Earlier this month, members dubbed the event a “sophomoric prank” and urged police to arrest the cyclists for breaking traffic laws.

In most instances, motorists angered by the riders vent their outrage by shouting curses and blaring their horns. Some, however, go further. In one incident last year, an impatient driver allegedly hit the gas and slammed into a cyclist holding a sign saying “Thank You for Waiting.” She was not injured, but her bike was crushed.

“They disrupt a lot of traffic, and people get steamed because this is peak drive time,” Officer Doug Clennell said as he prepared to mount his motorcycle and escort the swarm of cyclists at last Friday’s ride. “But they’re peaceful. I don’t have any complaints about that.”

It was Carlsson who conceived of the monthly rides in September, 1992. An avid cyclist, Carlsson commutes across San Francisco by bike and only bought a car when his daughter became too heavy to tote about on two wheels.

The term Critical Mass, Carlsson said, was plucked from a documentary on bicycling elsewhere in the world. It was used to describe urban cyclists in China, who must gather in significant numbers before they can safely cross busy intersections.

Fifty cyclists turned out for the first San Francisco ride, many of them bike messengers accustomed to the city’s narrow, traffic-clogged roadways. The crowd quickly doubled, then tripled. Last week’s ride--which included a hair-raising descent down the famous twists of Lombard Street--drew an estimated 1,500 riders.

“I know so many people who were inspired to try cycling because of this ride,” said Dave Snyder, executive director of the San Francisco Bike Coalition. “People want to ride, but a lot of them are afraid.”

They are afraid, cyclists say, because San Francisco, like many big American cities, can be a pretty inhospitable place for those seeking to navigate without gas-powered acceleration. The city, Carlsson said, “would be a great place to walk and bike if you weren’t fighting for your life on the road. This place is completely dominated by the need to move large numbers of cars through small spaces.”

Lisbet Engberg, a spokeswoman for the city’s Department of Parking and Traffic, said efforts are under way to make San Francisco more bicycle-friendly. Plans are afoot to create bike routes, re-stripe traffic lanes and install bike racks in parking garages.

But that, many Critical Mass devotees say, is not enough. The Bike Coalition favors the creation of a citywide network of “traffic-calmed” thoroughfares reserved for cyclists and pedestrians. The only cars permitted would be those owned by residents of the immediate neighborhoods.

In advocating such goals, San Francisco’s bicycle activists are in step with a nationwide explosion in bicycling. Over the past decade, the number of Americans who commute by bicycle has increased nearly threefold, to 4.3 million. Every state has a bicycle coordinator, and new laws permit the use of federal funds traditionally reserved for highways to be used for biking, pedestrian and transit improvements.

“People are rediscovering the bicycle,” said David Cohen, a Critical Mass rider and member of the Auto-Free Bay Area Coalition. “For years we’ve viewed it as nothing more than a toy. But it’s the most efficient machine we’ve ever made.”