In the wake of two incidents in which a piece of brake mechanism fell off train cars, WMATA says they've replaced nearly 300 friction rings on cars used throughout the Metro system.
Metro says that they inspected 464 rail cars from the 2000, 3000 and 4000-series and replaced 290 friction rings from brake systems that were showing wear.
Riders have become familiarized with the piece of equipment recently after the rings fell off trains and onto tracks twice in the past three weeks, causing evacuations of trains on the Blue and Orange Lines in the District on both occassions.
On Dec. 20, a friction ring fell off a Blue Line train near L'Enfant Plaza Station. Another train struck the piece of brake, causing a large portion of the area to close for hours; 300 people were also evacuated from a train that was stuck between L'Enfant Plaza and the Smithsonian Station.
After that incident, Metro inspected the brakes on its stock of 5000-series rail cars and found no new problems.
However, last Friday, another ring fell off a different train near the Stadium-Armory Station, causing passengers to be evacuated again.
No serious injuries were reported in either incident.