Total motor vehicle deaths peaked at around 50,000 per year during the period 1965-1975, but the current figures are more like 35,000 to 40,000, and that's with a larger population. Although a large fraction of these were undoubtedly due to drunken driving, it's still only a fraction.
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Also of note that, relative to total population or vehicle miles traveled, the fatality rate has been consistently going down. Thus, one's chance of being killed in traffic is lower than it's ever been.
Another interesting observation is that there was a sharp drop in motor vehicle fatalities during the Second World War (fuel rationing), and the period 1972-1978 (1970s energy crisis) and 2007-2011 ("Great Recession"). I guess maybe having a total World War, or at least a real bad depression/recession might help reduce traffic deaths more than banning cannabis or drunken driving.