Every San Francisco driver has thought about it in this congested, hectic city where scoring easy parking is rarer than a sunny day in July. It’s OK to double-park in the bus stop to fetch your dry cleaning or pull over in a transit-only lane right, right? Just for a moment?

A word to the wise: Don’t do it.

Unlike those infamous BART train cameras that don’t actually work, the more than 800 forward-facing cameras affixed to every San Francisco Muni bus work just fine. And last year, they led to a whopping 3,625 tickets to all those ne’er-do-wells who blocked a vehicle’s path.

Since the first cameras were tested in 2008 — they were made permanent on all buses in 2015 —there have been a total of 24,125 tickets mailed to owners of cars that were parked illegally or pulled over where a bus camera could photograph them.

The cameras are constantly running, and two Muni staff members have the riveting job of watching the footage and recording license plate numbers. Under a quirk in the state law, the footage can only be used to ticket parked cars, including those stopped with people still inside, but not for those driving where they shouldn’t.

Like every fine assessed by the city of San Francisco, the price tag is hefty. The current charge for parking in a transit-only lane or a crosswalk is $110, and stopping in a bus stop will cost you $288.

Muni spokesman Paul Rose said the cameras have led to fewer cars double-parking in front of buses and fewer commercial vehicles stopping in bus paths to unload. Though opponents of the cameras said they would violate people’s privacy, Rose said the agency hasn’t received a single privacy complaint since they went into use.

Assemblyman David Chiu, D-San Francisco, who sponsored the legislation making the forward-facing cameras permanent, said it was crucial to helping Muni buses pick up their pace.

“Muni has to go faster than 8 miles an hour,” Chiu said.

Oh, Assemblyman, don’t exaggerate. They go faster than that! The average speed of a Muni bus in 2014-15 was 8.1 miles per hour, according to a recent controller’s report — the slowest speed of buses of any city in the study, including Oakland, Seattle and Chicago.

Chiu is continuing his crusade to change road behavior with cameras. He recently introduced legislation that would allow San Francisco and San Jose to test a pilot program in which cameras would be used to ticket speeding drivers.

Chiu has an incentive to make the city’s roads as clear as possible. He commutes from his condo in the Candlestick Point area to Sacramento — and it can take 2½ hours or more during rush hour.

“The congestion on our streets and highways is crushing,” Chiu said. “We have to innovate new ways to move around efficiently, reliably and safely.”

The longtime bicyclist and Muni rider had to buy his first-ever new car for the grueling commute. It’s a Toyota Prius, and Chiu, being a good Democrat, picked dark blue.

Reason No. 8,572 San Francisco is the best — and quirkiest — city in the world: Quidditch class. Yes, families signing their kids up for spring classes with the city’s Recreation and Park Department can opt for the Muggle — er, nonwizarding —version of the game ripped from the pages of Harry Potter.

The instructor is Forrest Stone, a 29-year-old Sunset resident, who has worked as a lifeguard and swimming instructor for the department for years. It runs in his family: His dad, Andy Stone, supervises Stow Lake.

The younger Stone is a member of the Silicon Valley Skrewts, one of scores of real-life Quidditch teams around the country that play each other in tournaments.

Sadly, no one has figured out how the players can fly like Harry Potter and his Hogwarts pals, but the players do run around on brooms and try to launch balls through big hoops mounted on stands high in the air. The game is over when a player snatches a Velcro tail off the Snitch, a player dressed in yellow who tries to evade capture.

Stone said the sport translates well to kids’ rec classes because it promotes exercise and teamwork but also lures bookworms onto the field in a way baseball or soccer might not.

“There’s a joke in Quidditch that we turn jocks into nerds and nerds into jocks,” Stone said.

The class is for those ages 7 to 12 and takes place at 10:30 a.m. Saturdays starting March 18. It costs $42. Sign up starting Saturday on the park and rec website.

There’s a joke going around among city planners that if California wants to block President Trump’s wall along the Mexican border, it should offer to build it.

Think about it. How long did it take to get the new Bay Bridge built? Then-Gov. Pete Wilson announced in February 1997 that a new span would be constructed — and it opened in September 2013, 16½ years and three governors later.

Or look at the state’s high-speed rail — figuratively, of course, since there’s still not much to look at literally. The California High-Speed Rail Authority formed in 1996 and put a ballot measure before voters in 2008. Construction is progressing in the Fresno area, but the notion of a train whisking passengers from San Francisco to Los Angeles in a mere 2 hours and 40 minutes is still a far-off dream.

So perhaps California should say it will, ahem, “Build the wall!” as so many Trump rally attendees chanted. By the time that wall makes its way through the design and development process, the environmental review process, endless community meetings and the assured funding shortfalls, it’ll take easily more than a decade to build.

By that time, Trump will be back to holing up in his New York City tower, somebody else will be in the White House and California can ditch its wall plans and return to figuring out how to get that darn high-speed rail system built.

San Francisco Chronicle columnist Heather Knight appears Tuesday and Friday. Email: hknight@sfchronicle.com, Twitter: @hknightsf

Quidditch

Information may be found at the San Francisco Recreation and Park Department website.