In 1967, the UK's Road Safety Act made it illegal to drive with a blood alcohol level above .08. Watch the above clip from a TV news show on location in a bar where they interviewed some habitual drunk drivers just before the law was passed.
In the US, the first law that specified a blood alcohol concentration was passed in 1941. But the legal limit was (ahem) .15 percent. It wasn't until 2004 that the final state—Delaware—shifted to the .08 number that's now the legal limit across the country.
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