The findings come from the latest roadside survey by the National Highway Traffic Safety Administration based on breath, saliva, blood samples and questionnaires taken from randomly selected drivers in 300 locations around the United States. In 1973, 7.5 percent of drivers had a blood alcohol concentration of .08 or higher. (A level of .08 is above the legal limit in all 50 states.) In the latest survey, the percentage of people driving above the legal alcohol limit had fallen to 2.2 percent.The survey data showed that men were more likely to be impaired by alcohol than women. Drivers were most likely to be legally drunk between 1 a.m. and 3 a.m., compared with daytime or evening hours. The vehicles most likely to be operated by drunk drivers were motorcycles and pick-up trucks.The number of drunk drivers on the roads has fallen sharply during the past 30 years amid tougher laws, stiffer enforcement and a shift in societal views on alcohol, a government survey found Monday.The study found a higher risk of encountering drunken drivers in the early morning hours — 4.8 percent of drivers had an illegal blood alcohol level from the hours of 1 a.m. to 3 a.m. on Saturday. It found that 1.2 percent of drivers were legally drunk during the hours of 10 p.m. to midnight on Friday night, 1.2 percent of those surveyed were legally drunk while 0.2 percent were drunk during the daytime.