By Joe Shortsleeve, WBZ-TV

BOSTON (CBS) – There is a pretty simple law on the books in Massachusetts which says most vehicles cannot idle for more than five minutes.

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One viewer who uses the Back Bay T stop was frustrated because he witnessed buses idling for what he thought were excessive amounts of time. He wrote us, saying he felt this was unhealthy and a waste of money.

When the I-Team started doing surveillance looking for idling vehicles, we found a number of examples.

A maintenance van sat on Newbury Street, running but not moving for more than a half an hour.

A Federal Express truck idled on busy Centre Street in West Roxbury for five minutes.

We saw a number cabs on Commonwealth Avenue near Boston College chugging away for up to 25 minutes.

And yes, there were buses at the Back Bay station exceeding the five minute limit despite the presence of a “No Idling” sign.

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“Idling engines is a really huge problem for health,” according to Vanessa Green of the Diesel Cleanup Campaign. “Excess emissions are also contributing to lots of other chronic illnesses that people don’t often equate with poor air quality and exhaust. So there is also diabetes, cancer, heart attacks, strokes.”

Any number of agencies can enforce this law, including police, fire, and building and health inspectors. The I-Team couldn’t find much interest in enforcing this law, however.

Boston’s Air Pollution Control Commission is making an effort to curb idling. Program Manager Haidee Janak walks the crowded streets of downtown looking for violations.

The commission has issued a few violations, but in most cases, the fines were waived. Executive Director Carl Spector believes education, not punishment, is the best tactic. Another problem for enforcement is the violator must be monitored for at least five minutes before a ticket can be written.

“The nature of the law requires you to be in the right place at the right time,” explained Spector.

State Senator William Brownsberger of Belmont has filed a bill to limit legal idling to two minutes. One of the reasons is “two minutes will be a little easier to enforce,” he said.

The senator said he wasn’t surprised by the number of violations we found.

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Vanessa Green believes most drivers don’t realize how severe the consequences of idling can be. “Every time you are turning off your engine, you are saving somebody taking that extra breath which could be harming them.”