Leaving your car parked on the street can be a risky proposition in San Francisco, where a car is broken into about every 17 minutes.

Some people have even taken to placing "no valuables inside" signs in their vehicles in the hope that thieves will read it and move on.

A total of 17,970 break-ins were reported in the first six months of 2017, according to police, but the actual total is likely much higher; many victims never follow through and fill out online crime reports.

Photo: SpotAngels

Unfortunately, avoiding parking in a "bad neighborhood" won't ensure your driver's-side or passenger's-side window won't get smashed.

According to a new study by the parking app SpotAngels, none of the highest-risk blocks for break-ins in San Francisco lie in the neighborhood the app identifies as the worst for break-ins — the traditionally high-crime area of the Tenderloin/Civic Center/Downtown.

SpotAngels, which its co-founder describes as a "Google Maps for parking," helps people navigate the city's parking options, from public parking to metered and free spots, and gauge the ticket risk.

On Thursday, the app released a study comparing the number of break-ins in a neighborhood to the number of parking spots. The data, based on 2016 San Francisco Police Department reports, were used to pinpoint the worst blocks in the city for break-ins and the diciest hours during the week for parking on those blocks.

"The break-in risk is a big factor that has already been asked for by our users, like it would be cool to know how safe it is park here," SpotAngels co-founder Aboud Jardaneh told SFGATE. "Today, when you park, we send you a notification — the prices, the hours, when street cleaning is and all that. We want to include in neighborhoods where we think the data shows that it's less safe, that break-ins risk is higher on this street, keep your valuables out of sight."

The above gallery shows the 10 worst blocks for car break-ins in San Francisco in descending order. In addition, we included the worst blocks in five other neighborhoods with high rates of break-ins: Nob Hill, North Beach/Telegraph Hill, Russian Hill, the Financial District and Chinatown.

SpotAngel

Besides spotlighting the worst blocks, SpotAngels analysts also ranked the city's neighborhoods based on the incidence of smash-and-grabs, ranging from high to very low.

What they found, not surprisingly, is that thieves prey on vehicles in target-rich environments like easily accessed parking garages, large lots or areas of light foot traffic.

Wealthier neighborhoods did not necessarily enjoy a lower rate of break-ins. For example, Seacliff, home to some of the city's swankiest residences, ranked No. 5 in ratio of break-ins to number of parking spots, although a sizable number of the thefts occurred in the popular Land's End area near the Cliff House.

"The big takeaway here is that, even in a posh zip code, you shouldn't leave your valuables visible in your car,"Jardaneh says.