I have no problem legalizing it and regualting like alcohol. The only problem is we need something like a breathallizer to check pot intoxication levels for DUI.
About 12 years ago they were working on such a test, but they ran into a problem. None of the people they tested drove worse, and many of them drove better. The people doing the testing tried to hide the results, but the WHO found out about it and blew their stacks. They said that you cannot do medical research and hide the results because they were not what you wanted them to be.