

New signs are in place at stations along the Silver Line. (Robert Thomson/The Washington Post)

This post has been updated and corrected.

So what exactly is the hold up, Post readers asked (and have been asking) since we reported news last week of an agreement between the Metropolitan Washington Airports Authority and Metro that could mean the beginning of Silver Line service this summer?

The 11-page agreement between the MWAA and Metro outlines the list of tasks that must be completed before passenger service can begin. They range from the mundane — installing locks on rollup doors at one of the stations in Tysons Corner, to the significant — fixing the automatic train control system to ensure that trains receive the proper speed signals and don’t stop unnecessarily.

Some are jargony — “Ceiling intersection guard for escalators” or “reclosure of the traction power gap breaker.” Others are more straightforward: “Elevators Piston Inspection: MWAA shall have inspected all elevators to confirm that there are no additional oil leaks or issues.”

But all have one thing in common: “These are issues we want to have addressed before passenger service can begin,” Metro spokesman Dan Stessel said.

Here are details of some of the other work that must be completed before Silver Line trains can start running.

Much has been made of the hundreds of speakers that must be ripped out and replaced because they did not meet fire code. That work must still be completed.

The following three items are related to train reliability.

During testing, MWAA officials found issues with “loss of speed read outs’ in Silver Line trains. Essentially, signals are picked up by sensors on trains that will display a two-digit number two numbers to the train operator, which reflects the maximum speed a train should be traveling as well as the optimum speed it should be moving given where it is in the system and the position of other trains around it. A “loss of speed read out” occurs when the numbers move to zero, causing the train to stop — even though there is no reason for it to slow. If this happens, a train operator must contact the operations center for clearance before the train can move again. If this happens too often, the system can back up causing delays. MWAA must ensure that adjustments to the system have been made to prevent this from happening.

Another issue that must be resolved before passenger service can begin is related to “bobbing track circuits” that send incorrect messages that a train is on the track when it isn’t. A false signal such as this also will cause other trains in the area to stop until train operators make contact with the operations center. MWAA will be required to put a short-term fix in place in the track circuit area where this is a problem. A longer-term fix will involve converting some track circuits from audio frequency to AC single rail power frequency.

Metro also is asking MWAA to improve the reliability of circuit breakers in some sections along the rail line that could affect third-rail power.

We hope this helps gives readers a sense of what MWAA’s contractors will be doing in the next few weeks.