SAN FRANCISCO (KGO) -- The first of San Francisco's new red light cameras was activated Wednesday at a busy downtown intersection. There'll be a lot more coming.All of them replacing the old cameras that were breaking down.Red light runners... they're hard to miss here on busy Fourth and Harrison -- a main artery to Highway 101.But starting Wednesday, a red light camera will be watching you.First, there'll be a 30 day warning period.Municipal Transportation Agency spokesman Paul Rose says, "So, if you run a red light at this location, you'll receive a warning but after 30 days, these warnings will turn into actual citations."A citation for running a red light these days is close to $500.This is the first of some 20 cameras that'll be installed at 13 intersections by the end of the summer."From our point of view, they can't come soon enough and we need more," says Brian Wiedenmeier, who is with the San Francisco Bicycle Coalition.He remembers when there were some 47 red light cameras in the city. The first cameras were installed in 1996.Rose says, "Since 1996, we've seen a 66 percent drop in injury collisions related to red light running across the city."The MTA's contract with the company that made them finally expired.The cameras were old. Parts were hard to come by."They did break down more often. We saw a less amount of citations coming from these cameras over the last few years," adds Rose.The city quietly shut all the cameras off in January.So, for more than three months, red light runners got a pass.But now with a new company, the cameras are state-of-the-art and more reliable.And they save lives, says Wiedenmeier."This is about addressing the most dangerous behaviors on our streets. And that's running red lights and failing to yield to pedestrians and people on bikes."