"Slow down, you're doin' fine" may be some of Billy Joel's best advice, but when it comes to the T... it's not exactly what we're all thinking.

In an effort to eliminate the notorious "slow zones" thanks to speed restrictions, the MBTA announced plans to shut down portions of the Red, Orange, Green, and Blue Lines starting later this month.

Why are there speed restrictions?

Speed restrictions — which impact 31.1 miles of subway line in total — were put in place due to problems with the track that could impact passenger safety.

There are two types of speed restriction: Line-wide, which force slowdowns across an entire line, and Block speed, which only apply to specific lengths of track.

So, they're shutting down (more) lines?

For a few days at a time, portions of your favorite line may be shut down. The shutdowns will provide time for the MBTA fix parts of the track that cause slow zones, whether that be:

Replacing old rail ties and tie plates
Replacing the entire track
Improving power delivery systems

The first shutdown will impact the Green Line and take place between North Station and Kenmore Station, Nov. 27-Dec. 5 + between Riverside and Kenmore stations, Dec. 11-Dec. 20. This will be followed by work on the Red, Orange, and Blue Lines in 2024.

View the full shutdown schedule.