A hobbyist tracked SF parking enforcement live by predicting ticket numbers

On September 23, 2025, software engineer Riley Walz — known for stunt websites — launched Find My Parking Cops, a site styled like Apple's Find My that showed the real-time trails of San Francisco parking control officers. The idea came from his roommate's parking fine: Walz noticed each ticket carries a nine-digit citation number, figured out the numbers are predictable, and realized he could scrape them efficiently.

The pattern, he wrote: add 11, except add 4 if the last digit is 6 — so no ticket can end in 7, 8, or 9. The stakes were real: San Francisco issued over a million tickets last year, more than $100 million in fines, with street-sweeping violations running $90 each.

Because officers apparently claim batches of ticket numbers, every newly issued citation plotted on a map traced that officer's route through the city. A car owner could watch the activity of patrols and see if any were descending on their neighborhood — before walking out to move the car.

The site went viral the day it launched and worked for a few good hours. Then the real-time data feed went dark: "In rare lightning speed, the SF government changed their site within hours of this site going live," Walz announced on the site. An SFMTA representative said citations "ensure compliance with parking laws" and that the city welcomes "creative uses of technology" but needs its employees able to work "safely, and without disruption."

Citation IDs advance by a fixed rule (add 11, add 4 if the last digit is 6), so polling the public feed reveals each officer's route as tickets land

Citation numbers are sequential and predictable, so the public ticket database can be enumerated as fast as officers write tickets.

Officers appear to draw batches of ticket numbers at shift start, which links number ranges to specific patrols and routes.

The site only re-plotted data the city itself published; no infiltration was needed.

The city re-engineered its site within hours — indirect confirmation that the map was reading something real.

Sequential IDs are a privacy leak: anything numbered in order can be enumerated. And institutions fix accountability tools at the speed of embarrassment — the feed died within hours.

The feed was cut the same day the site went live, and Find My Parking Cops stopped working. Walz documented the method in a blog post, and the episode became a case study in how quickly public bodies will reconfigure data exposure when it is turned into real-time accountability.