Des Moines police released data for the first time Monday showing a decrease in collisions in the areas where the cameras were placed in June 2011.
They compared the number of accidents at the 5 intersections and I-235 from 2009 – 2012 and overall, accidents have gone down.
"We'd like to see, obviously, a reduction that stays in this vicinity over time. Only time will tell at this point," said Sgt. Jason Halifax.
He said the numbers are encouraging and validate the need for them on streets.
For example, this intersection at MLK and School had 16 collisions in 2009, 22 in 2010 and just 5 last year. The change was not so significant at 9th and Grand, which had 8 in 2009, 3 in 2010 and 4 last year.
"If you don't speed, you don't run red lights, the tickets won't be affecting you," Halifax said.
Traffic camera critics are glad accidents have decreased but say some data actually shows red light cameras can increase collisions.
"You have a flash going off. You have a distraction while going through the intersection," said Sen. Mark Chelgren, R-Ottumwa. "You have people worried about getting a ticket so they're slamming their breaks on which causes a rear-end accident for the person behind them."
He also questions all the variables.
"How much to attribute of that to the traffic cameras versus how much to attribute that to the weather patterns? With one set of data points, it's too early to make that decision," he said.
Even if collisions went to zero due to traffic cameras, Chelgren said he still wouldn't support them because they don't allow you to face your accuser or have due process.