BOSTON -- How safe is the public transit system that so many of us travel each day?

Team 5's Sean Kelly looked into the MBTA safety records and history of MBTA crashes.

Consider the fact that hundreds of thousands of people use MDTA commuter trains every week without problems and you'd have to say the safety record is very good.

Looking back at the history of accidents, however, it's typical for one train to be stopped when a crash occurs.

The Green Line has had more than its share of collisions over the last two decades.

One, in 1990, when one train rammed into the rear of another at the Arlington Street station, hurt 33 people, although there were no fatalities.

Investigators determined that the 64-year-old driver who caused it had a blood-alcohol level above the legal limit.

Five years later, another collision at the busy Copley Square station. Once again, a trolley rear-ended another car that had stopped. Thirty-two people were hurt but no one was killed.

The NTSB determined the female driver who caused it failed to follow posted speeds and never applied the brakes.

Until Wednesday’s Newton crash, the most recent serious collision involving passengers happened in March.

That's when a runaway freight car from a lumberyard slammed head-on into a commuter train in Canton.

It had by far the highest number of casualties at 150, although most injuries were minor.

MBTA investigators determined the driver likely saved lives by halting his train to avoid a bigger crash.

As bad as all of those collisions were, none matched what MBTA passengers saw in January 2007.

Their commuter train traveling through Woburn, Mass., hit and killed two track workers.

NTSB investigators determined a dispatcher forgot about the work crew and failed to warn the driver.