Portland Train Speed Limited by Extreme Heat

Portland’s MAX trains must slow down after temperatures hit 100 degrees, reports Anthony Macuk for KGW.

According to Macuk, “TriMet has upgraded the system in recent years to maintain full speed at higher temperatures, but there's still an upper limit.” After 100 degrees, MAX trains will slow down to a top speed of 35 miles per hour, while WES trains will top out at 40 mph.

At 105 degrees, the WES trains stop running. If temperatures get that high, TriMet may adjust or suspend service on MAX trains, but that decision is made based on conditions throughout the system and out of consideration for the safety of riders and employees.

As Macuk explains, “MAX trains are powered by overhead wires, which have to be kept taut so the train's pantograph arm can maintain steady contact. But the wires are made of copper, which expands when heated and can cause sagging.” If the sagging causes the lines to sink too low, trains have to slow down or stop entirely.

WES trains face a different problem, one that could impact Amtrak and other train systems as well. “TriMet's WES trains are diesel-powered and run on Portland & Western freight rail tracks with no overhead wires, but they can still get tripped up by heat waves because the high temperatures can also cause the steel rails to expand and temporarily deform — a phenomenon called ‘sun kinks’ — making it unsafe to drive trains over them at full speed.”