His findings: 2.7 seconds.
"Not even three seconds," he says.
Three seconds, when every other yellow light on the stretch of road was four seconds long. In other words, as he drove the street, the yellow lights in order lasted four, four, four and out of nowhere three seconds.
"It's a blink of an eye - a $70 blink of an eye," says Irving.
Many communities around the country are using cameras to try to stop drivers from running red lights. It's a safety issue, yes, but drivers like Irving are say it's really about making money for local governments.
Why this light in Bethesda was three seconds might have a million dollar answer. Literally. This one traffic camera earned the county $1 million in fines over 14 months.
"It shocked me," he says. "And the only explanation for it is that light is a trick. And law enforcement shouldn't be a trick."
Lon Anderson of the Triple A's mid Atlantic office complains too many traffic cams today are money scams for the cities that put them up.
Washington D.C. collected big on an odd double yellow light that turns red when it's not even at an intersection. In Baltimore, Anderson says, you can get a red light ticket by missing the light by one tenth of a second.
These systems can work, but why can't they work without tricking them? Why can't they work without gimmicks?
But County Executive Doug Duncan calls traffic cameras essential in an era when red light running is rampant.
"These are not traps, these are not tricks," says Duncan.
He says the cameras reduce red light running 40 to 70 per cent.
"Its a way to make people safe," says Duncan. "We put those cameras up at the intersections that are most dangerous."
Still, Duncan won't defend the three-second light.
When asked why that light is three seconds, Duncan laughs then adds, "I don't know, it should be the same as everywhere else."
He says he plans to change it.
Two days after CBS News taped this interview - and a year after Irving first complained, the county set all the lights on the stretch at 3.5 seconds. The county keeps to its belief the cameras are for safety -- so it plans to keep the $1 million.