The lifespan of that DSTT curve

The south portal at Westlake Station, photo by Oran

One of the major features of the recent 1-Line maintenance was the replacement of the northbound track between University Street and Westlake stations. This segment boasts the sharpest curve in the system, and as a result, the most worn down rails. The resulting wear-and-tear meant a fairly bumpy ride in that section, even at slow speeds.

Long-time transit enthusiasts will remember that the rails in the tunnel are not that old. The original track from when the tunnel first opened was not compatible with Link's modern specs and was stripped out during the 2005-2007 tunnel closure. Although it's generally recognized that rails in segments with lower-radii curves have reduced lifespans, the northbound University Street-Westlake curve did not even make it to twenty years.

A month-long reduced service period every 15-20 years is not the worst disruption a system can face, but according to Sound Transit spokesperson John Gallagher, this came earlier than anticipated and should not be an example for the future:

The original rail was installed in 2005/2007 as part of the tunnel retrofit for light rail. While the tracks met specs, there were some issues at the time of the installation. For example, during pre-revenue grinding, the rail grinder derailed and gouged the rail. We welded it to repair it, but this was a problem section of track for a long time. The new section was installed without any problems, so we anticipate that it will have a normal life span of about 25 years.

For now, no other extended Link closures or disruptions are expected in the near-term. With any luck, the new tracks will make it to a quarter-century before the next major maintenance disruption.