As some trains rolled along at 50 miles per hour Friday, 10 miles per hour faster than they previously could safely run, MBTA General Manager Phillip Eng pledged that "This is just the beginning."

For the first time in decades, Red Line trains are now running at 50 mph. It’s full speed ahead for trains on the Braintree branch. NBC10 Boston was the only station there as the first trains of the morning reached their maximum speed of 50 mph between North Quincy and Braintree.

On the MBTA, the typical Red Line train stretches six cars. But in select circumstances, riders could now see just four cars when their train arrives at the platform.