In a single month, the District of Columbia took in just under $26 million in revenue from its ubiquitous traffic cameras. And, no, that figure wasn't a typo when The Washington Examiner published it Tuesday.

To put that staggering sum in perspective, it is more than twice the $12 million taken in last January. In fact, the District took in only $55 million from these cameras for the entire fiscal year of 2011. The revenue stream is likely to keep growing. The District government will add 134 more of these cameras over the course of this year, more than doubling the size of its existing network.

With each such effort, the District just builds the case that these cameras are nothing more than a cash cow for government. Does anyone still buy the argument that safety is the reason?

When smartphone apps began to appear last year to alert drivers to camera locations, the city began using smaller, mobile cameras hidden in shrubbery or designed to look like utility boxes.

City officials, including the mayor, have claimed all along that the cameras are all about public safety. They point to the fact that the District had 19 traffic-related fatalities last year, down from 32 the previous year. The cameras, they argue, are getting people to drive slower.

It's a reasonable enough proposition, but as any scientist or logician can explain, correlation does not prove causation. What proof do we have that the cameras are responsible for this decline? More than a year ago, The Washington Examiner made Freedom of Information Act requests to the District to provide the raw data documenting before-and-after crash statistics at the intersections and along highways where the cameras are deployed. That data ought to settle the matter. We are still awaiting a response, and no, we're not holding our breath.

There is some evidence the effort to keep the money flowing in is causing corruption, too. Twenty-two-year D.C. police veteran David Cephas admitted in court last year that he deliberately falsified his certifications that the photo's radar equipment had been properly calibrated.

Meanwhile, the amount of money that the city takes in grows and grows. As does the District's reputation as one big speed trap.