One thing that's often irked the roughly 2% of the population that regularly ride light rail here is the fact that when the temperature climbs into the 80s and 90s, the two-car "trains" slow to a crawl - or stop completely. For 30 years, the former transit agency (now a development agency) known as Tri-Met has explained this as "sun-kink".
As temperatures rose above 90 degrees Fahrenheit throughout August, the city's Metro Area Express (MAX) light rail system reported severe service interruptions across its entire network. Trains were forced to slow to a crawl or sit idly in between stops, leading to drastically extended commute times and a flurry of angry online comments directed at TriMet (Portland's largely taxpayer-funded public transit authority).
TriMet has explained that the delays were the result of a phenomenon known as "sun kinking," which is when higher-than-usual temperatures cause rail and power lines to expand and buckle, forcing trains to reduce speeds or stop running altogether.
In heat, the rails expand lengthwise, but when they've maxed that out, they start to buckle sideways, and that can derail a "train". So far, so good. But it doesn't happen in Phoenix, where it gets a lot hotter. It doesn't happen in Seattle, which has approximately the same weather that we have. You might wonder why.
The answer, it seems, is that those cities anchored their tracks to concrete, whereas in Portland, they chose to use gravel beds. Of course, heavy rail uses gravel beds as well, and they don't seem to suffer from the problems that Tri-Met's light rail lines routinely experience. In any case, Tri-Met went with gravel, presumably to save on costs.
Phoenix, Arizona, routinely sees temperatures far in excess of Portland's. However, its Valley Metro light rail service has proven immune to heat-related service delays. Valley Metro Public Information Specialist Ann Glaser writes in an email that Phoenix's system has been able to avoid such problems by setting its tracks in concrete and calibrating its power cables to withstand high temperatures, things she says it was able to do without a significant increase in construction costs.
Seattle did the same thing, and despite having temperatures in the 90s periodically, they've had no heat-related delays.
TriMet is currently experimenting with limited fixes to the most severely affected areas of track. However, networkwide fixes are still years away. But that didn't stop the agency from spending some $1.49 billion on the new MAX line completed in September 2015 that—you guessed it—was built with the same rail-on-gravel design, ensuring sun-kink-caused delays will be a summertime ritual for even more commuters.
This will no doubt frustrate Portland's small businesses, who pay an average of $10,856 per year (and rising) in taxes to support TriMet. One wonders how successful those small businesses would be if they, like the transit authority, hiked their prices while providing sporadic service to customers.
Unfortunately, the businesses can't impose arbitrary tax hikes on agencies like Tri-Met; that's a one-way street: from private enterprise and other taxpayers to government agencies. But no worries - Tri-Met has great plans to ram a $2 billion set of light rail lines through the "southwest corridor", from downtown Portland to the upscale Bridgeport shopping center in suburban Tualatin.