Handing out parking tickets is big business for the City of San Francisco – to the tune of some $134 million a year.

And there are oh-so-many ways you can get one of those citations, given the city’s complex and expanding set of parking rules. (For example, did you realize that you now have to feed the meters all over town on Sundays?)

Luckily, a new smartphone app (for iOS and android) called Park.IT, has a built-in SFMTA parking regulation interpreter that is regularly updated to help you avoid some of those tickets.

“We help people follow the law,” says co-founder and CEO Calvin Liu. “There are so many categories of parking rules -- meter rules, commercial rules, inclined parking, red, white, yellow zones, driveways, residential time limits, street sweeping, and so on. We fold all of those rules into one app.”

When you enter an address into the app, it shows you all the nearby parking spots and (if they are metered) how much they cost per hour. This latter feature is helpful in case you find yourself trying to park at one of those confusing new meters with dynamic pricing that cost up to $5.50/hour.

Park.IT also alerts you when it’s time to move your car or replenish the meter.

“We ask how much money you put in meter and send you notices when it is about to expire,” explains Liu, “or when any other rule is about to be violated.”

Park.IT uniquely has integrated the inclined parking rules into its databases, since 40 percent of the city’s streets are over the 3 percent grade that triggers the restriction that you must curb your front wheels in the appropriate direction, depending whether the car is facing uphill or down.

“We had to gather all of this data ourselves because it does not exist in a usable form from the MTA,” says co-founder Manohar Kamath.

The two-man team started mapping the city’s streets in 2010 with pen and paper, noting block by block all the parking rules that applied.

“There are 32,500 street sections in San Francisco, 25,000 of which can be parked on at least some of the time,” says Liu. “There are in total 250,000 rules that apply.”

Once they had enough data, they automated, establishing a system that can map out other downtown areas quickly and efficiently.

“Now we can do things like map eight square miles of downtown LA and Santa Monica in just three days,” says Liu.

Park.IT has worked closely with the City government here while building its app.

“The City has been very receptive,” says Liu. “They know we’re not a radar detector. We're trying to help people understand what the law is so they can follow it. That helps everybody.”

Liu says new residents are among those who can benefit the most from Park.IT.

“When you first come to San Francisco, you have to attend what I call 'Parking Ticket U' and pay your tuition,” he says, only half-jokingly. “On average, the people we talked to said that can cost them $1500/year. San Francisco is the third highest collector of revenue per car among all U.S. cities.”

(Philadelphia, he says, is the highest.)

Park.IT is poised to expand beyond San Francisco, and expects Washington, D.C., another city with a confounding set of parking rules, to be one of its next markets.