In Los Angeles, Drivers and Bicyclists Learn to Coexist Monica Almeida/The New York Times The fourth CicLAvia event, which closed 10 miles of Los Angeles streets to car traffic, drew nearly 100,000 bicyclists. LOS ANGELES - It was a warm April morning in downtown Los Angeles, and there was not a car on the road. For five hours, the streets were commandeered by nearly 100,000 people on bicycles - old and young, wearing spandex and silly hats, dogs and babies perched on handlebar baskets - in a celebration that produced a sight that once would have seemed inconceivable in this city of cars. It was the fourth time this city closed its streets for the event known as CicLAvia, and it was the largest one yet. These days in Los Angeles, there are midnight bike rides, East Side bike rides, women's bike rides and nude bike rides rolling out nearly every day. In the past 18 months, close to 40 miles of bike paths and lanes have been created across the city and the City Council passed a measure to prevent bicyclists from being harassed by motorists. On one recent evening, drivers came to a (mostly) uncomplaining stop as swarm after swarm of cyclists breezed through an intersection on Wilshire Boulevard, complete with a police escort. And on Tuesday, there was a "Blessing of the Bicyclists" - with a rabbi, a water-sprinkling priest and bikers in attendance - at Good Samaritan Hospital, which has treated its share of injured bikers over the years. Bicycling is no longer the purview of downtown messengers or kamikaze daredevils. Its advocates include hipsters who frequent the bicycle repair cooperative known as the Bicycle Kitchen (which, experiencing growing pains, is about to move to bigger quarters) and middle-class riders who hum along a bike path on the beach in Venice and Santa Monica. There are biker-commuters who like to shock people by boasting that they do not own a car. And the mayor, Antonio R. Villaraigosa, who broke his elbow in a bike accident involving a taxicab and has since become one of cycling's biggest cheerleaders, is intent on resurrecting a plan that he acknowledged had been "kind of languishing a bit." For years, bicyclists in Los Angeles were just another renegade subculture in a city that is teeming with all manner of subcultures. These days, they have become downright mainstream. "I can't keep up with all the group rides out there these days," said Damien Newton, the founding editor of Los Angeles Streetsblog, which champions bikers and pedestrians. This isn't a side thing anymore. It's definitely out of the shadows and out of the subculture. None of which is to say that this of all cities is about to give up the car for the bicycle. But at a time when Los Angeles is struggling to ease congestion - and when cities from New York to Portland, Ore., are outpacing this city in making life easier for the urban bicycler - the bicycle is becoming part of the transportation fabric in Los Angeles. "There was not a biking network when I was there," said Janette Sadik-Khan, who attended Occidental College here in the late 1970s and today is New York City's transportation commissioner, leading the way in expanding a network of bicycle lanes. You are beginning to see the bones of one emerging now, and it's very exciting. Bicyclists have long complained that the Police Department blamed them in any conflict involving a car and gave cyclists tickets for even the most minor infractions. So consider this message posted by the group Midnight Ridazz after its most recent ride: "The Midnight Ridazz would like to extend a sincere thanks to the L.A.P.D. and especially to the officer (whose name we did not get) who recently helped to escort our ride through the streets of Los Angeles." Mr. Villaraigosa said he wanted the city to establish 40 miles of bike lanes and paths a year, a policy inspired by his own "nasty spill" dodging a taxicab and a part of his effort to cut back on automobile use here. "No question about it: bike ridership is up dramatically in L.A.," he said. You see it all over the city. For anyone who lives outside Los Angeles - and even for many people who live in Los Angeles - the notion of taking a bicycle to the roads here would seem someplace between daring and suicidal. And with some reason: two years ago, a doctor was sentenced to five years after being convicted of assaulting two bicyclists by slamming on his brakes during a confrontation in the Brentwood neighborhood. The resentment goes both ways, as Hector Tobar of The Los Angeles Times said in a column last summer that was generally supportive of bicyclists. "People can be as reckless on a bike as they are behind the wheel of the car," he wrote. But stupidity with no steel around you to protect you is a more naked, brazen kind of stupidity - and that's what drives a lot of Angelenos batty.