V.  RESULTS AND DISCUSSION

Connecticut Roadside Survey

H. Driver BACs by Time of Night, Age, and Gender

The proportion of drivers with positive BACs increased steadily throughout the night from a low of 6.4 percent between 9 p.m. and 10 p.m. to 16.6 percent from 1 a.m. to 2 a.m.  Sobriety checkpoints generally began between 8 p.m. and 9 p.m., and data collection generally began shortly afterwards.  The proportions listed below only included BACs of drivers tested at times that matched across all sobriety checkpoints held in a particular location throughout the study.  The proportion of positive BACs at higher levels increased steadily throughout the nighttime hours until 2 a.m.  Most of the drivers with positive BACs had BACs less than .05 across all times of night.  The 1-2 a.m. hour had the highest percentage of positive BACs and also included the highest proportion of drivers with BACs above .05 and the highest proportion of drivers with BACs at or above the legal limit of .08.  In total, only 1.1 percent of the 3,356 drivers interviewed by researchers had BACs at or above the legal limit. The results are reported in Table 31.

Table 31. Connecticut Roadside Survey: Distribution of Roadside BACs by Category and Hour of Night

Generally, as the age group of the drivers increased, the proportion of positive BACs increased as well.  This trend did not include the age group including those 65 years old and older.  This age group had the lowest proportion of drivers with positive BACs.  In general, there were more positive BACs for drivers of all ages measured after the July 4th holiday enforcement period.  BACs decreased from the pre-July 4th holiday period to the post-winter holiday period in every age group except the 16- to 24-year-olds.  More drivers 35 to 49 years old came through the sobriety checkpoints than any other age group.  Drivers in the 25- to 34-year-old age group were the second most common. Results are presented in Table 32.

Table 32. Connecticut Roadside Survey: Distribution of BACs by Age Group

As indicated in Table 33, the proportion of drivers going through the sobriety checkpoints from younger age groups increased slightly during later hours.  The proportion of drivers at sobriety checkpoints from the youngest group, drivers 16 to 24 years old increased throughout the night from 22 percent from 9 p.m.-10 p.m. to a high of 32 percent from 1 a.m.-2 a.m.  The proportion of drivers from the 25- to 34-year-old age group remained relatively stable throughout the night.  The proportion of drivers from the 35- to 49-year-old age group dropped from above 30 percent before 1 a.m. to 26 percent from 1 a.m.-2 a.m., meaning that the shift in the age of drivers at later hours was due to a decrease in the number of drivers from this older group along with an increase in the number of drivers 16 to 24 years old.

Table 33. Connecticut Roadside Survey: Proportion of Drivers at Sobriety Checkpoints by Age Group and Hour of Night

As indicated in Table 34, the proportion of male drivers with positive BACs at sobriety checkpoints decreased significantly from 17.8 percent for the pre-July 4th to 10.6 percent for the post-winter holiday period (χ 2(1)=10.42, p<.01).  Female drivers had positive BACs about the same percentage of time from the pre-July 4th holiday period (9%) to the post-winter holiday period (9.3%).  There were generally more male drivers going through the sobriety checkpoint locations during all survey periods, and they generally were more likely to have positive BACs, but the proportion of men drinking and driving decreased almost to the same rate as the women by the post-winter holiday period.

Table 34. Connecticut Roadside Survey: Distribution of BACs by Gender