I don't see why any drug should be considered illegal. We should all have the ability to do whatever we want to do with our own bodies. That's why we're fighting against the weed laws, and we should extend that to all substances, since it's not a crime if nobody gets hurt except for, potentially, the willing participants.

The argument that it would cause chaos on the roads is fallacious. People don't stop doing drugs just because they're illegal. Any pot smoker should know that for any drug the demand just doesn't go down with government intervention in our lives. The supply is just moved into an underground black market, sometimes involving violent criminals, instead. Drug use has gone up substantially throughout the whole War on Drugs, so it's obvious to anyone with a working brain that treating addictions as crimes rather than as a public health problem isn't doing jack shit.

The main reason intoxication causes death on the roads is not so much that we have these intoxicating substances in our society, but rather that our society has devised its transportation system in such a way that we get ordinary and often incompetent people controlling individual metal boxes at high speeds all over the place, rather than some mode of collective transportation which would be far more fuel-efficient, safer and less harmful to the environment. The promotion of the automobile as the chief mode of transportation was done primarily to profit large and influential corporations such as those involved in automobile manufacturing (a lot more money can be made selling every family a car every few years than by running an efficient public transportation service) and petroleum (same idea, consumption and thus demand go way up when everybody drives individual vehicles).

It's a simple fact that automobiles are more profitable to corporations, which is the only reason any large-scale projects happen under capitalism, and that is why we have them, even though they are extremely inefficient and unsafe especially when compared with alternative possibilities for transportation networks. We do not need to abolish drugs to stop the resulting car crashes from happening; we should abolish the car-based transportation network. No matter what you try to do, people anywhere will be at varying levels of consciousness. Some will be alert, some will be tired, some will be distracted, some will be sober, some will be stoned, some will be drunk, some will be angry, and some will be just plain stupid. You get the idea. Perhaps it would be a better idea to put our transportation in the hands of trained professionals (who would of course lose their job if found working while intoxicated), rather than making all those people of varying levels of competence careen around really fast in their own big iron boxes if they want to get from point A to point B.