The first scientific investigation of how alcohol affect driving ability were conducted in america during the 1930s. measures of blood alcohol concentration showed that drivers who were involved in fatal crashes often had high levels of alcohol in their systems. about half of the drivers who were involved in fatal crashes had been drinking large amounts of alcohol.of the other drivers who were stopped at the same time and places as the accident only a few had drunk enough alcohol to give them blood alcohol levels above 0-1 per cent