PHILADELPHIA (CBS) – We don’t need to tell you that it only takes one snafu on the roadways to really screw up your commute. But it’s not an accident or weather conditions that have been snarling traffic on two highways and a bridge of late.  And there’s no telling when it might happen next.

“That darn traffic light at the top of the ramp is not working once again. It’s flashing red,” KYW traffic reporter Sam Clover exclaimed in one recent report.

That light and ramp we’ve been hearing about is at the 30th Street exit from the Schuylkill Expressway.

“Lately, we’ve been having some power issues,” said Steve Buckley, deputy streets commissioner in Philadelphia. “There’s low voltage through there, and the city, PECO, and PennDOT are working collectively to see if we can resolve the issue.”

When the signal doesn’t get all the juice it needs, for safety’s sake it becomes a virtual stop sign — flashing red.  But it also leaves drivers seeing red as I-76, the Vine Street Expressway, and the Ben Franklin Bridge quickly get clogged as cars stack up at the chokepoint.

“The city’s in the process of pursuing some battery backup systems for intersections where we do tend to have recurring problems,” but Buckley says but that could be six months away.

They’re working on a permanent fix and in the interim can use generators when that light goes on the fritz.

Reported by Ian Bush, KYW Newsradio