Parking, which is horrible everywhere in San Francisco, is especially horrible on a certain block of Townsend Street.

“This is the block from hell,” Sema Unlu said as she poured quarter after quarter into the slot on the parking meter that never seemed satisfied until it had gobbled every last coin in her purse.

Unlu had landed a parking spot on the 300 block of Townsend Street, between Fourth and Fifth streets. According to a new survey of parking ticket data, it’s the most ticketed block in San Francisco. Meter minders wrote 4,380 tickets there last year — about 400 more than any other block in town.

It figures, say the motorists lucky or unlucky enough to find a parking space on the Block From Hell.

There are parking signs, and rules, that seem in conflict with one another.

The other day, some signs were missing, and a temporary no-stopping sign was ripped in half. Some spots seem almost schizophrenic — they feature red no-parking curbs but also have parking meters. There are bus zones, motorcycle parking zones, a taxi stand for cabs waiting at the Caltrain station, a few fire hydrants and two stops set aside for the double-decker Megabus interurban line.

The Megabus, incidentally, can take you to Los Angeles for a dollar. At that rate, you would have to travel to Los Angeles 84 times to equal the cost of one San Francisco parking ticket.

As for parking in the evening, the rules change completely when there is a baseball game or concert at nearby AT&T Park. At such time, the Block From Hell becomes part of the “special parking zone” surrounding the ballpark, and meter rates soar higher than pop flies, to $7 an hour, or $35 for the whole ballgame. (That comes to 140 quarters.)

So it was no surprise that Unlu was just a bit terrified to have found a spot for her black sport utility vehicle in the middle of the block. Unlu, who with her husband manages a Mediterranean restaurant a half mile away, was there to deliver a large box of catered gyro sandwiches and kebabs to a nearby office.

“My husband sent me down here a half an hour early, because of the parking,” said Unlu, who said it’s almost as hard when you find a parking place as when you don’t. The parking meter for her spot was one of those large blue boxes that control seven other spaces, too.

A motorist must remember that he parked in Space No. 4 and then pay at the blue box, and hope he put his money in the correct blue box and not the blue box that controls another space No. 4 just a few steps down the street.

And then there is Space No. 6 linked to Blue Box No.2.

Space No. 6 is a yellow zone, which means it’s a loading zone. Except that it isn’t, because of two signs on a pole planted next to Space No. 6.

The first sign says Space No. 6 is a no stopping zone from 7 to 11 a.m. Mondays through Saturdays, except for commercial trucks, and that cars in violation can be towed. Another sign, just below the first one, says the space is a passenger loading zone from 11 a.m. to 11 p.m. and there is a five-minute limit, and cars in violation can be towed. Outside of those hours, parking is apparently OK, unless it’s “special parking zone” night because of a ballgame.

Luck, which has so much to do with living a satisfactory life, is intimately involved with the Block From Hell. The other day, Bob Zepernick didn’t have any.

Zepernick, 66, drives a delivery truck for Patatas, a Chilean restaurant. He pulled into a yellow zone at the east end of the block. A small sign said, “Passenger loading only, 11 am-11 pm, Mon-Sat, 5 minute limit.” He switched on his emergency flashers. He figured he could get away with stopping for a 10-minute delivery.

Motorists who turn on their emergency flashers, thinking it will save them from a parking ticket, are known as dreamers. To a meter minder, an emergency flasher works something like a candle for a moth.

“There’s nowhere else to go around here, with the construction and all,” Zepernick said. “If I’d known it was such a big ticketing place, I wouldn’t have parked here. But there’s no parking around here for cars.”

It was a big ticketing place, all right, and Zepernick’s big ticket will cost him $110.

Zepernick, an Oakland resident, said his company usually sends two people if the delivery is in a place where tickets are dished out frequently, like the Block From Hell. The second person stays with the car or drives around the block. The cost of hiring a second person to help do a one-person job is still cheaper than the cost of a San Francisco parking ticket.

“We will be sending a second person next time we make a delivery on Townsend,” Zepernick said. He added that he sure hopes his boss will split the payment of the $110 ticket with him. But most delivery drivers know that they’re on their own for parking tickets.

In two years, he said, he’s received two parking tickets on the job.

“I’ve been lucky,” he said.

A few steps away on the Block From Hell is a meter that says it’s OK to park from Monday to Saturday from 9 a.m. to 10 p.m., at normal variable rates, and that it’s OK to park from noon to 6 p.m. on “special event Sundays” (at not-so-special rates), but that if you park in the spot from 6 to 9 a.m. on Monday through Friday, it’s a bus zone and your car will be towed away, for a minimum charge of $391, plus $59 a day for “storage” if you don’t ransom your car within four hours.

The Block From Hell is not the only woeful place to park in San Francisco, only the worst, according to a study by the people who run the SpotAngels parking app, a service that monitors parking charges and towaway zone times for overwhelmed motorists.

The company crunched all the parking tickets issued by San Francisco last year and identified the 10 most ticket-prone blocks in San Francisco. After the Block From Hell, they include four blocks of Mission Street, two blocks along the Embarcadero and one block on First and on Fourth streets. All are located in the South of Market area.

Parking in a street cleaning zone was the most common type of parking ticket (540,000 issued), followed by parking meter violations (214,000 issued) and residential parking violations (129,900 issued).

The best neighborhood for parking, according to the SpotAngels study, is Twin Peaks, where there are often no restrictions. From downtown, however, it’s a 5-mile walk uphill back to your parked car.

Michael Cabanatuan and Steve Rubenstein are San Francisco Chronicle staff writers. Email: mcabanatuan@sfchronicle.com, srubenstein@sfchronicle.com Twitter: @tuan, @SteveRubeSF