Drive hammer get nailed, an electronic display board seen on American highways, who knows what it means?

"drunk driving, never be soft"

note:

1. Hammer means "seriously drunk"

"Being hammered" means: (adjective) drunk as a fiddle.

Get Nailed (colloquial usage) means "arrest" or "conviction"

Being caught means being caught or possibly being convicted.

This is the first warning sign set up on the highway in Washington state many years ago, and later several other States followed suit.

This has been the mantra of the Washington State Patrol for years, sending a clear message to drunk drivers: We will not let you go.