From time to time, publications have appeared on the effect of alcohol on the driving efficiency of operators of motor vehicles. Attempts have been made to correlate the amount of alcohol in the blood, urine or expired air of drivers in traffic accidents and to determine the lowest quantity of the intoxicant in blood, urine and expired air above which it would be reasonably safe to infer that an impairment of reactions and reflexes would occur. Among the observers who have studied this problem are Schwarz,1 Heise,2 Carlson,3 Naville and Rosselet,4 Turner5 and Selesnick.6 The Committee on Tests for Intoxication of the National Safety Council7 has recommended that "all persons having a level of alcohol in the blood above 0.15 per cent by weight are sufficiently impaired to be unsafe drivers." With the exception of work by Gerber,8 who found a blood