One day of every month a massive group of bicycle riders assembles in downtown San Francisco in order to ride around the city as a group of cyclists so huge that it gets to take command of the streets and intersections.

“Critical Mass” began seventeen years ago in San Francisco as a monthly ride to assert bicycle rights and the idea has since spread to hundreds of other cities. It is prominently known for being a leaderless group. No agenda is set, other than the time and place for the start of the ride.

The politics of cycling aside, I thought it sounded extremely fun to ride all around a beautiful city as part of an unconventional parade, so I encouraged my wife and thirteen year old son as well as my college buddy John to join me for a ride this last month.

We lucked into an unusual warm and comfy day in San Francisco. Across from the Ferry building we joined a big crowd of cyclists all sitting and standing around waiting to begin. Most of the bikes were pretty standard but a few had things like banana seats and chopper handle bars. There were some recumbent bikes and even some unicycles. One bike was surrounded by about thirty balloons. There were several nude guys standing around waiting to ride; one guy wore only a codpiece. Several bikes were equipped with a booming sound system for tunes. It was a party all right.

Sometime after six o’clock the group started out by first circling a couple blocks in the Embarcadero area and then moving out through the financial district. The pace was mellow and there was enough space around each rider that it was easy to relax. Just make sure you keep your tire out of any sunken streetcar tracks running down the middle of Market Street!

The mass of cyclists was several blocks in length, with at least a thousand riders (maybe two thousand or more on this balmy day) that typically took minutes to pass through an intersection. The traffic lights would turn red and the bikes just continued to flow through. Cars waited through multiple traffic-light cycles, most were patient, others not so much. It was like some sort of bike riding heaven where cars wait while the bikes have their way for once. Occasionally a car honked in frustration and the cyclists would erupt with sarcastic cheering.

Somehow this leaderless multitude made its way through the city. My son Wesley, never that happy to just hang back in exciting situations, got permission from us to proceed to the front, while Melody, John and I remained back in the big group, content to ride alongside whomever happened to be near us, which, for a time was a guy with a suitcase-sized sound system with 12” speakers playing Michael Jackson and Marvin Gaye tunes. Nothing quite like coasting downhill in the shade of twenty-story tall buildings while everybody grooves to a good bass line.

Later Wesley told me about how it was at the front of the pack where decisions were made by various different guys who would yell or urge a left or a right. Some strange dynamic was at work in which some yells were ignored and others were heeded. (According to Wikipedia, Think-tanks have studied Critical Mass for insights into “leadership by network.”) At one point my son, though young and a newcomer, called a right turn and the multitudes followed. (You go, Wesley.) Later a group at the front that was going too fast proceeded straight through an intersection and was, in effect, “punished” when the others took everybody else on a left turn and left the speedy ones having to double back.

I learned about all this action the following day when I asked Wesley about it. From my point of view at the time, with blocks of riders stretched out before me and blocks of riders trailing behind, it was all a fun party.

What’s not to love about it? It was an unusual opportunity for a relaxed bike ride down the middle of streets through a city renowned for its urban form and architectural interest. Melody and John and I would occasionally drift apart and then find each other to exchange comments like “gorgeous Vic on the left” or “check out the cutest deco building ever.”

Some riders around us were saying things like “I hope we go to the beach.”  They said it sort of loud, as if that was how you shaped your destiny in the mysterious world of Critical Mass decision making, by wishing it out loud.

We ended up cruising down through Hayes Valley and biked along the panhandle of Golden Gate Park and then through the park itself – all with great visuals. It seemed we were heading to the beach after all. In the park the throng of riders stretched out, things mellowed, and the encounters with cars were much less. We didn’t need to be massed solid anymore to function safely. We passed the fringe of a Pearl Jam concert, glowing in the twilight from a nearby valley in a sort of unreal and dreamlike way. We rode past the peculiar sight of teenage boys trying to scramble under temporary cyclone fences while cops on horses rode along the fence after them.

B y the time we got to the beach, the other-world quality was complete. Most of the cyclists had somehow mysteriously disbursed. Before us were the last remnants of a flaming red sunset and a massive beach on which numerous campfires and bonfires glowed with tribes of humans gathered around them in the growing darkness. It was like something from the cover of a “Yes” album from the seventies, except real and three dimensional.

“I think I need to touch the water,” I said to my mates as we watched thunderous waves crash in the distance. All agreed, so we locked up the bikes and ventured on foot to the glowing orange of water’s edge, a proper terminus for our big adventure.

Though we had to ride back through the city at night without headlamps, it turned out just fine. We selected a lightly trafficked avenue with street lights and four-way stops – problem solved. There were moments riding down tree-lined streets past well-lit cafes with sidewalk dining that the city felt just like Paris to me.

In this way we passed a memorable evening. The lesson for me seems obvious, but sometimes isn’t: Remain open to adventures large and small. Go after the opportunities. Trust in the fun.