Concerns about San Francisco’s decaying light poles were ignited Monday night after one corroded by urine toppled onto a car, narrowly missing the driver.

The three-story-tall lamp post at Pine and Taylor streets snapped around 6:30 Monday and landed on a nearby car, almost crushing the driver. No one was injured.

A perfect storm of conditions rusted out the base of the pole, San Francisco Public Utilities Commission officials say, and caused it to fall. At the time, the lamp post, which was already old, was damaged by urine and weighed down by an oversized banner.

“We believe there was some contribution of dog or human urine on the base of the pole,” PUC spokesman Tyrone Jue said. “It has actually been an issue for us in the past. We encourage people and dogs alike to do their business in other places, like a proper restroom or one of our fire hydrants, which are stronger and made out of cast iron.”

Urine accelerates the corrosion of the metal base of street poles, he said.

The PUC has long known that its light poles are aging and becoming dilapidated. Last year, the street light budget increased tenfold from $500,000 to $5 million for maintenance and replacement of the poles.

The PUC recently launched an assessment program to visually check on every single light post — all 25,000 of them. So far, 100 street lights have been replaced along San Bruno Avenue.

People can also report aging posts by calling 311 or downloading the app SFStreetlights.

— Lizzie Johnson

E-mail: cityinsider@sfchronicle.com, ljohnson@sfchronicle.com Twitter: @sfcityinsider, @lizziejohnsonnn