A Blue Line train sits at the bottom of an escalator at O'Hare International Airport after it derailed and overran the platform early this morning. (Handout)

A Blue Line train sits at the bottom of an escalator at O'Hare International Airport after it derailed and overran the platform early this morning. (Handout) (March 24, 2014)

All U.S. transit agencies that operate rail systems received a federal alert Thursday to conduct tests ensuring adequate stopping distance of trains in emergency-braking situations, to avoid the risk of a crash similar to the CTA wreck at the O’Hare station three months ago.

The “urgent safety concern’’ was raised by the Federal Transit Administration as the result of the ongoing investigation by the National Transportation Safety Board into the collision and derailment in the early hours of March 24 in which a Blue Line train traveling about 26 mph jumped the tracks and smashed into an escalator after the train’s operator dozed off, officials said.

The safety board said an automated braking system activated, but it failed to stop the train before it collided with bumper posts and other end-of-line equipment. About 30 people were injured.

The FTA on Thursday urged the nation’s rail transit systems to ensure enough space is available for trains during emergency braking to safely stop in terminals; to immediately evaluate automated signals and trip stops under actual operating speeds; and to resolve any deficiencies if insufficient stoppage space is identified.

“Speed restrictions, reconfiguring automatic signals and trip stops, modifying the placement of performance of bumping posts and installations, and recalculating safe braking rates are all steps that rail transit agencies can take to address this critical safety concern,’’ FTA Deputy Administrator Therese McMillan said in a letter accompanying the safety advisory.

After the Blue Line accident, the CTA lowered the speed limit of trains entering the O’Hare station to 15 mph and it moved the fixed trip stop back to provide more stopping distance.

jhilkevitch@tribune.com | Twitter: Twitter @jhilkevitch