HB - 1841, Establishing Minimum Train Crew Size on Certain Trains, was enacted into state law, on June 11, 2020, by Governor Jay Inslee.  

The State of Washington has maintained a Passenger Train Crew Law, enacted on March 21, 1911. 

An important thing to understand is that Class I Freight Railroads were once regulated under the Interstate Commerce Commission, whose operational description was categorized as a Public Utility. This allowed for state residents with train crew laws, to vote 'for' or 'against' when State Voting Initiatives were filed by the Association of American Railroads in each state with crewing laws in order to reduce their numbers through the ballot box.
 
Class I railroads have been privatized since the Staggers Act was passed by the days Federal Administration in the 1980's, which is why each state now has the ability to protect the safety of its citizens safety from private industry and are able to establish train crew size without the concern of federal preemption. 

For an illustrative understanding provided by the Brotherhood of Locomotive Engineers and Trainmen - Washington State Legislative Board, Chairperson / Legislative Director - Shahraim C. Allen, please click on the following link below.

Article: https://www.freightwaves.com/news/washington-state-will-require-a-minimum-train-crew-size

Exerpt from HB 1841 - “The legislature finds that adequate personnel are critical to ensuring railroad operational safety, security, and in the event of a hazardous material incident, support of first responder activities, as well as in the interest of the safety of passengers and the general public. Therefore, the legislature declares that this act regulating minimum railroad employee staffing to reduce risk to localities constitutes an exercise of the state’s police power to protect and promote the health, safety, security, and welfare of the residents of the state by reducing the risk exposure to local communities and protecting environmentally sensitive and/or pristine lands and waterways.”