Wash. Rev. Code § 81.53.080
After February 24, 1937, no building, loading platform, or other structure which will tend to obstruct the vision of travelers on a highway or parkway, of approaching railway traffic, shall be erected or placed on railroad or public highway rights-of-way within a distance of one hundred feet of any grade crossing located outside the corporate limits of any city or town unless authorized by the commission, and no trains, railway cars or equipment shall be spotted less than one hundred feet from any grade crossing within or without the corporate limits of any city or town except to serve station facilities and existing facilities of industries.
The commission shall have the power to specify the minimum vertical and horizontal clearance of under-crossings constructed, repaired or reconstructed after February 24, 1937, except as to primary state highways.
RCW 81.53.080