Boston's transit system has reached a $1.5 billion, four-year contract with its carmen's union.

The MBTA says the contract will save it $80 million dollars over the next four years and more than $750 million over the next 25 years.

The agreement also reforms overtime and other work rules to lower MBTA costs, the transit system announced.

Overtime will only be granted to workers if they've already reached 40 full hours of work for that week.