The U.S. Coast Guard and the Pacific States/British Columbia Oil Spill Task Force 
endorse a system of voluntary measures and minimum distances from shore for certain 
commericial vessels transiting along the coast anywhere between Cook Inlet, Alaska, 
and San Diego, Califronia.  See U.S. Coast Pilot, Chapter 3 for details:

Based on the West Coast Offshore Vessel Traffic Risk Management project, which was 
co-sponsored by the Pacific States/British Columbia Oil Spill Task Force and U.S. 
Coast Guard Pacific Area, it is recommended that, where no other traffic management 
areas exist such as Traffic Separation Schemes, Vessel Traffic Services, or 
recommended routes, vessels 300 gross tons or larger transiting along the coast 
anywhere between Cook Inlet and San Diego should voluntarily stay a minimum distance 
of 25 nautical miles offshore.  It is also recommended that tank ships laden with 
persistent petroleum products and transiting along the coast between Cook Inlet and 
San Diego should voluntarily stay a minimum distance of 50 nautical miles offshore.  
Vessels transiting short distances between adjacent ports should seek routing guidance 
as needed from the local Captain of the Port or VTS authority for vessel groundings and 
resulting oil spills in the event of a vessel casualty.