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.
Got another burning question you’d like us to sleuth out an answer for? Hit us here.
The real reason is the gap in the tracks where the lift span meets the fixed span. It’s about 3 inches wide. Listen the next time you cross on MAX: ka-THUNK ka-THUNK…ka-THUNK ka-THUNK. That’s the wheels of the train hopping over the gaping hole in the tracks leading straight down to the river. If they went any faster the train might not land back on the track.
When they built Interstate MAX, there was a line item in the Final Environmental Impact Statement to close the gap and increase the running speed to 25 mph. That was determined to be “infeasible” according to the engineer I talked to at an open house a year or 2 ago.
I feel edified.
OK, but why does the HEAVY RAIL go much faster then?
Yeah, but how come we can’t climb to the top and drink 40s anymore?
Heavy Rail doesn’t go that much faster, I think it is also limited to about 15-20 mph. But also the construction on the steal bridge that TriMet/Portland/Metro has done to the above sections is much more feeble than the lower heavy rail section. The bridge is maintained by UP and was built originally to act as the main bridge into town for the railroad. The light rail on the upper deck and walkways on the side are all additions since the bridge was created.