Metro's platform sign problem
For several weeks, Metro riders have been telling me they think there's something wrong with the platform signs that display train arrival times. I've been getting complaints about the electronic signs for years. The most common complaint is that the sign says the next train will be eight cars long and it turns out to be six.
But the new complaints are different. First of all, there have been a lot of them. Second, they focus on errors in the arrival times. They say the signs show a train boarding when it left several minutes earlier, or that the signs show a train three minutes away when it is at the platform.
Metro spokeswoman Lisa Farbstein says the transit authority knows there's a problem but hasn't been able to figure out the cause yet. Metro refers to the situation as a latency problem. Data about the train movements are delayed getting from one point to another within the passenger information display system.
"It appears the issue is with messages backing up in the PIDs server," Farbstein said in an e-mail. "These latency issues typically occur during rush hour when there are lots of trains and lots of rider messages being displayed. Our IT department is analyzing the situation to determine the solution."
Farbstein said that so far the tech people have been able to figure out that the system is generating accurate predictions of train arrival times. So the problem appears to occur after the computer system makes the prediction and before it gets displayed on the platform signs.
Here are a couple of messages I got from riders during my online chat Monday:
Q. Metro Message Boards: For over a week now the Metro message boards have been out of sync on the Red Line. The sign may indicate a train is arriving or boarding when there is no train in sight. The arrival times have been off about two minutes (if it says 3 minutes it really is 1 minute).
Q. PIDS: They've been screwed up on the Orange Line too. I arrived at my station the other day only to find out that the train that was supposedly arriving was already gone.
Here are a couple of comments that have appeared here on the blog:
"My orange line train was supposedly 4 minutes away last night as it arrived in the station."
"The train arrival boards at Farragut West and Federal Center SW are also out of sync with the actual trains."
David Alpert also has written about the PIDs problem on his Greater Greater Washington blog. And UnsuckDCMetro wrote about The Crazy PIDs These Days.
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