These two routes have a short concurrency in Pullman, but they're so short, they're not signed. I'm just curious if anyone knows which is the primary route. (Like SR 20 is the primary route in the SR 20/21 concurrency.)
Looks like it's 270, according to WSDOT's online GIS map of state route mileposts:
(https://i.imgur.com/MTtbsCs.png)
(The selected point in the table belongs to SR270 MP 2.3, and is highlighted on the map within the concurrency)
This appears to be due to the fact that SR 27 previously began at the north end of the SR 270 concurrency (so SR 270 was there first). You can see evidence of this on the map since there is a milepost 2B on SR 27 south of the SR 270 concurrency (the B indicates a realignment or extension), and then the mileposts reset to 0 after the concurrency.
I don't completely understand the explanation, but the short answer is that SR 270 is primary route in the concurrency!
So thank you! LOL