New York City is changing rules and speeding up some of its trains in an effort to improve subway service.

The New York Times reports that New York City Transit increased train speeds on two lines in Brooklyn from 15 mph to as much as 30 mph over the weekend. The agency’s president, Andy Byford, plans to speed up other lines in the coming months.

Officials instituted strict speed rules for safety reasons following serious crashes in the 1990s. That contributed to system delays.

Byford says efficient signaling will allow trains to travel safely at higher speeds.

A “speed unit” created by Byford has recommended 130 locations where speeds should be increased.

(AP)