To go after those pesky signs illegally placed along Miami-Dade County’s main thoroughfares — think “We Buy Junk Cars” and “We Fix Computers” — the county’s building department took a page from the political playbook:

Flood the repeat sign offenders with robocalls. Annoy them enough that they will comply with the law.

To an extent, the unusual tactic has worked. The building department has issued more than 1,100 illegal-sign citations since the robocalls began a year ago.

A recorded message tells listeners that the only way to stop receiving the automated calls is to contact the building department, where the caller is matched with the phone number and promptly issued citations for however many of his or her signs the county has removed.

The department has more than 200 telephone numbers on its current list. Each is called every day during business hours, about once every 45 minutes.

“Some of them answered and said, ‘You’re driving us bananas,’ ” said Charlie Danger, the county’s building chief.

In Broward, Hollywood initiated a similar program this year. One target of the robocalls, who posted “We Buy Houses” signs, was so miffed that he filed an ethics complaint against the city’s mayor. (The complaint was thrown out.)

In Miami-Dade, some of the fines, for hundreds of illegal signs, run into the thousands of dollars. But only about 230 of the citations have been paid. The county has filed personal liens against 10 or 15 people with outstanding bills.

And some of the sign posters have wised up to the system — they’re now changing their phone numbers about once a month to avoid the robocalls. Building enforcement officers have yet to come up with a plan to deal with those shrewd operators.

Tracking violators of Miami-Dade’s sign ordinance, which prohibits them on public rights-of-way, is notoriously difficult, Danger said. They often pop up overnight on medians, fences, stop signs, light poles and traffic poles, particularly along main streets such as Kendall Drive, Bird Road, Coral Way and the Gratigny Parkway.

And it’s not just drivers who notice them.

“We had almost every commissioner calling, ‘When are you going to get rid of the signs?’ ” Danger said.

Angry business owners complained, too. Among them was Ricardo Lopez, who runs a computer-repair shop in Miami and said he had to shutter his second location in West Kendall.

“This guy got me out of business,” he said of whoever posted “We Fix Computers” signs around the Miller Square shopping center at Miller Drive and Southwest 137th Avenue, near Lopez’s now-closed shop. “I spent too much money ... trying to do it legally.”

As the building department brainstormed the best way to attack the problem, one of its employees brought up the subject at her house over dinner. Her son, a lawyer, suggested a novel idea: What about robocalls?

The department already had an automated phone system to communicate with people with pending permits. So the calls began.

“This message is from Miami-Dade County,” the recording begins. “Remove all signs immediately, or you will be subject to a citation of up to $500 per sign.”

The call includes a phone number for listeners to set up an appointment and come in to the building department to sign an affidavit promising not to post more signs.