You have to watch closely for it, but every day a timeless cat-and-mouse game unfolds on the streets of Toronto, one in which the mice never learn their lesson, and the cats always bring in a big prize.

In this case, the mice are the hundreds of courier drivers who scurry around the downtown core every day in their trucks and vans, getting and delivering precious packages. The cats: the parking police.

Courier companies are Toronto's biggest parking violators. Of the top five ticket recipients in 2006, three were international couriers: Federal Express, United Parcel Service and Purolator.

The list, according to city records, was rounded out with two car rental companies, but those violations were committed by individual renters.

In 2006, the three couriers together compiled 33,716 tickets, worth approximately $1.5 million. That's about 130 tickets every workday, or roughly one ticket every four minutes during business hours.

But for the couriers, the fines are simply an unavoidable cost of doing business. They have no intention of parking legally. The city has no intention of halting the ticketing.

On a recent bright morning around Yonge and Bloor Sts., there were two or three couriers parked on every block. Like Purolator's Ed Rushford. When asked about the parking police, he sets down his parcels and blinks through black-rimmed glasses. He disconcertingly resembles an angry Michael Douglas in Falling Down.

"I've had more tickets in the last year and a half around here," seethes the 54-year-old, "than I have in the last 29 years."

He says police now "wallpaper" courier vans with tickets. "It makes us look bad, those things flapping on the windshield. We're just trying to make a living."

As he talks, two parking officers swish by on bicycles going in the other direction. "It's not about parking," he continues. "It's about revenue generation."

And the city does makes big cash on parking violations, about $80 million every year.

The couriers all know the parking police who work their neighbourhoods. They know the easy-going ones, the mean ones. They text message each other as to the whereabouts of the particularly overzealous cops.

Conversations between drivers and parking cops are often strangely amicable, but sometimes there's tension. Rushford relates how, a few days prior, he was approaching the end of his shift and had four tickets already.

One young officer, whom he talks to regularly, walked by and didn't ticket. When Rushford returned, however, a fresh, yellow violation glared out from under his wiper. He confronted the officer, who, according to Rushford, said he was "below his quota" for the day.

One Toronto officer, who asked not to be named, said there isn't an explicit quota, but officers are expected to write 65 tickets each a day.

"It's an uneasy relationship," Rushford explains. "It's like the bird that cleans the crocodile's teeth."

He means that sometimes, the croc will let you go. Sometimes he'll bite.

"With the amount we pay," echoes UPS courier Corey Ferrara, 27, "this country should be out of debt."

Of course, the drivers don't themselves pay. They bring the tickets back and hand them over to the company to look after.

Drivers say they're not asked to find legitimate places to park. "The company would lose more money if we had to wait to find parking," says one FedEx driver who asked not to be named. "The packages would be late."

Of the companies, only FedEx responded to questions, but wouldn't discuss specifics. "We try to balance meeting the needs of our customers, their reliable, on-time deliveries, with the traffic restrictions in each city," says spokesperson Karen Cooper. "But in very congested cities this is often difficult."

The companies, says Anthony Fabrizi, manager of the city's parking operations, "treat tickets as well as anything else related to driving around as a cost of doing business in Toronto."

In 2002, he says, the city adopted a "zero tolerance" policy between 7 a.m. and 7 p.m. toward parking on main arteries. This meant no mercy for couriers.

In Toronto, the courier companies still come in each week with their hundreds of tickets, Fabrizi says, "and literally flip through each ticket" with staff, to see if there are any errors.

That's probably by necessity. Though a big business expense, the fines aren't tax-deductible.