I will take exception to the thrust of this thread, because I know that foreign ships are a major, major contribtor to pollution in So.CA. Long Beach, CA accepts 40% of all shipped US goods, and filthy foriegn flagged ships belch a huge amount of pollution there.
There is room for improvement in maritime laws, all the way around. Flag nations like Nigeria need to have their ships reigned in.
How many cars and trucks versus the number of ships move each day in Souther CA? In terms of fuel consumed or energy used, I suspect ships isn't even in the margin of error in comparison to land vehicles.