From the SDOT website RPZ page:
SDOT recently completed a parking study of residential streets in Wallingford to determine the occupancy in the area as well as the percent of non-resident parking throughout the day and evening. The study area includes the existing Zone 5 and parts of existing Zone 22, as well as many currently unrestricted blocks. SDOT studied the area holistically and presented results to the Wallingford Community Council on September 6. […]
For an area to qualify for a new RPZ, there must be at least 20 contiguous blockfaces that are 75% or more full of parked vehicles with at least 35% of those vehicles belonging to non-residents. Our Wallingford parking study found that weekdays during daytime hours were when the most blocks met the occupancy criteria.
That’s no surprise to me. Every morning, I see commuters from up north arrive, park their cars close to the Wallingford / U District border, and then walk in (rather than pay for parking closer to the UW). I usually have to drive a couple blocks away from my house to find a parking spot after 8 or 9 am. Evening time is no problem.
More information on the study and its finding on SDOT’s page, as well as a link to a survey, which closes November 30th.
(Thanks Alex Okubo for the tip!)