Temps cool down but improvements to keep MAX trains running on time heat up


Trains running on MAX Blue, Red and now Yellow lines run at regular speeds in up to 100 degree heat

MAX Yellow Line riders will be the next to benefit from improvements made by TriMet maintenance crews when the thermometer soars this summer. Reducing heat-related delays is part of our continuing efforts to speed up transit and keep trains running on time as we get people efficiently to their jobs, home and adventures.

Our crews have improved the overhead wire and counterweight system on the MAX Yellow Line between Expo Center and Interstate/Rose Quarter stations. They’ve also installed equipment to keep the rails in place as they heat up. These are the same improvements that they made on the MAX Blue and Red lines to keep trains running at normal speeds until temps hit 100 degrees. Next up for the work will be the Green Line between Gateway Transit Center and Clackamas, and then sections of the Orange Line.

Combating science with determination

Transit agencies build their light rail systems for the average operating temperature of their region. Here in Portland, MAX was built to work best in a relatively mild climate, with average temperatures ranging from around 40 to 70. As our summers have heated up, our maintenance crews are taking on Mother Nature.

Rails are made of steel and can expand by several inches in extreme temperatures. That can cause them to swell and bow, which is commonly called a sun kink. On extremely hot days, the rail can be 20 to 30 degrees hotter than the air. By installing rail tie anchors in kink-prone areas, our crews have found the rail stays in place.

The overhead power wires on the MAX system are made of copper, which will expand and sag as temperatures soar. Counterweights help keep the wire taut, but in extreme heat the wire expands so much that the counterweights hit the ground, allowing for the sagging. Our crews found that by replacing rectangular cast-iron counterweights with round ones there’s more room for movement to maintain tension on the wires. They also adjusted the calculation for the tension needed as temperatures change, which has kept the overhead wires from sagging too much.

Improvements keep WES trains running on time

Like the improvements to keep MAX trains running on time when temperatures rise above 90 degrees, TriMet crews worked with Portland & Western Railroad to keep WES trains running at regular speeds longer. Crews stabilized the rail and the bed underneath them by replacing the ballast, removing vegetation and elevating curves. Those improvements, along with installing Positive Train Control, mean WES trains will not have to slow down until the thermometer hits 100.

Extreme heat still requires operating changes for safety

Some temperatures are so extreme that we will need to slow or stop train service for the safety or our riders and to prevent damage to the transit system. So here’s our high heat cheat sheet:

  • MAX
    • 90-100 degrees
      • Orange Line trains between Tilikum Crossing and SE Park Ave Station must reduce speeds by 10 mph in higher speed areas. Expect about 15-minute delays.
      • Green Line trains between Gateway Transit Center and Clackamas must reduce speeds by 10 mph in higher speed areas. Expect about 15-minute delays.
    • 100 degrees
      • All lines reduce speeds to no more than 35 mph. Expect up to 30-minute delays.
  • WES
    • 100 degrees
      • Trains reduce speeds to no more than 40 mph. Expect up to 20- minute delays.
    • 105 degrees
      • Train service suspended, per Portland & Western Railroad restrictions, and shuttle buses will serve the line. Expect major delays.

Plan ahead

When the temps soar again, TriMet encourages riders to stay hydrated and plan ahead. Check trimet.org/alerts before you head out. All our buses and trains have air conditioning, but when waiting for a vehicle to arrive, stay in the shade if possible. Check trimet.org/alerts or @trimetalerts on Twitter before you head out. You can also sign up for alerts about your bus or train via email or text message at trimet.org/email.