In an off-topic comment to a post yesterday, a reader asked this:
Why does the MAX go over the bridge suuuuuuuuuuuuuuuper sloooooooooooooow now between the Rose Quarter Transit Center and downtown? Didn't used to. Is it because the bridge might collapse at any moment?
Good question! I put it to TriMet's Mary Fetsch, who put any bridge-collapse fears to rest, and explained why the trains have always crossed the Steel Bridge with caution:
It's not that the bridge will collapse, of course. However it does have to do with the structure & how a heavy object like a train moving over it affects it. There are switches, bridge lift and lowering stops, and electrical supply systems for the train motors on the bridge that can be affected with too much vibration. Possibly other systems are affected as well.
Operationally, there are curves and fairly steep slopes just prior to and after the bridge when approaching from either direction. On these curves & slopes are signals and rail switches that we need to have operators be cognizant of.
As to the claim itself about trains running slower now than before ... The train speed over the bridge has always been 10 mph. This hasn't changed.
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