of North Carolina
"2 out of 3 .00 BAC"
The University of
North Carolina at Chapel Hill (UNC) is a public, four-year university
with a total student enrollment of 24,180 (15,400 undergraduate and
8,780 graduate and professional students).
In the fall of 1997
and 1999, teams from the North Carolina Highway Safety Research Center
collected breathalyzer data from University of North Carolina students
who were returning home to fraternities, sororities, residence halls
and apartment complexes. Data were collected between the hours of 10
p.m. and 3 a.m. on every night of the week for 6 weeks. Two-thirds of
the interviews took place on Thursday, Friday and Saturday. A total
of 4,381 students participated in the two studies: 1,846 in 1997, and
2,535 in 1999.
Funding for this
project has been provided by:
- The National
Highway Traffic Safety Administration
- The North Carolina
Governor's Highway Safety Program
- The U.S. Department
- The University
of North Carolina's Division of Student Affairs
To develop a more
complete understanding of student alcohol use on the UNC campus in preparation
for a program to reduce excessive or dangerous drinking.
Data were collected
on 20 nights between October 2, 1997 and November 14, 1997, between
10 p.m. and 3 a.m. on all nights of the week. Randomly selected groups
of individuals were approached by a single member of a four person interview
team and asked if they would participate. Once consent was obtained,
all members of two- and three-person groups were interviewed. For larger
groups, three individuals were randomly selected for interview. The
interview took approximately 4 minutes and requested information about
activities during the night, drinking (where, when, what, how much),
perceptions about alcohol use among students, mode of transportation
and ways used to avoid drinking and driving. Drinkers were asked whether
they felt any effects and to estimate their blood alcohol concentration
The sampling procedure
was designed to obtain a representative sample of students at a large
public university who were returning home in the evening. The campus
was divided into five geographically distinct routes along which interview
teams walked. These routes passed every dormitory, fraternity, sorority
and private dormitory on or near campus. The sampling plan was developed
such that every residential location was visited at least six times:
once before and after midnight on week nights (Sunday through Wednesday),
Thursdays and weekends (Friday and Saturday). On each night that data
were collected, three interview teams worked, covering separate routes.
Respondents were sampled in the vicinity of student residences. To avoid
attracting too much attention, interview team moved continuously between
residences, typically collecting data at a single location for no more
than 10 minutes.
the undergraduate student body lives on campus. In order to obtain information
about those who live in private residences interviews were also conducted
at five large apartment complexes that, according to university records,
house a large concentration of university students. At these locations,
the interview procedure resembled that typically used in roadside surveys
(Foss, Beirness & Sprattler, 1993). Individuals were interviewed
at entrances to the apartment complex while they remained in their vehicles.
An initial screening was used to avoid interviewing non-students.
Of the 2,530 persons
contacted, 2,186 (86.4%) cooperated, and 2,023 (80%) completed the interview
and provided a breath measurement; 109 (4.3%) declined the interview,
but did provide a breath sample, and 54 (2.1%) did the interview but
would not provide a breath sample.
sampled on campus were interviewed regardless of their student status,
results presented here represent only those 1,846 individuals explicitly
identified as students enrolled at UNC. A breath alcohol measurement
was obtained for 1,790 (96.9%) of these individuals. Data presented
here are not weighted to account for differential probability of selection.
Accordingly, estimates of overall use for the campus must be considered
tentative. Subgroup comparisons are likely to be less sensitive to varying
likelihood of selection. The table below shows the full BAC distribution
for the three times of the week studied.
Concentration by Time of Week
* Results are
reported here in mg/dL, which is the preferred measure in international
forums. A BAC measure of 20-49 mg/dL is equivalent to our BAC measure
of .02-.049; a BAC measure of 50-79 mg/dL is equivalent to our BAC measure
.05-.079, and so on.
A follow-up study
was conducted in 1999 (n = 2,535). A comparison of survey results obtained
in 1997 with those obtained in 1999 revealed:
- A 9% increase
in the number of students who returned home with a .00 BAC on Thursday,
Friday and Saturday. (65% of students were found to have .00 BAC in
1997, while 71% had a .00 BAC in 1999: a six percentage point increase,
equaling a 9% increase overall.)
- A 30% decline
in the percentage of students who returned home with a high BAC (over
.08%). (13% of students were found to have a high BAC in 1997, whereas
only 9% did in 1999: a four percentage point drop equaling a 30% decline
Note: The "2
out of 3 .00 BAC" campaign had only begun about one month before
the follow-up survey conducted in 1999. Therefore, the reductions noted
above cannot clearly be attributed to the social norms campaign only
The combined data
(years 1997 and 1999, n = 3,953) indicate that 49% of respondents would
be classified as "binge drinkers," where that is defined as
those (both men and women) who self-report the consumption of 5 or more
drinks at an occasion at least once within the last two weeks. Interestingly:
- Although they
reported consuming 5 or more drinks on an occasion at least once during
the last two weeks, nearly 50% of these so-called "binge drinkers"
had zero BACs on the night they were interviewed.
those who self-reported "bingeing" (defined here as the consumption
of 5 or more drinks for men/4 or more drinks for women) on the night
of the interview:
Another BAC study
will be conducted in the fall of 2002.
Methods Employed and Primary Normative Messages
Note: The "2 out of 3 .00 BAC" social norms campaign
was begun in 1999.
Posters and zipper
pulls with the message "2 out of 3 .00 BAC." In addition,
numerous cash incentives are offered as a way to encourage students
to know and retain the normative message, and to spread the word about
it. For example, every week the "prize team" randomly selects
student residence hall rooms, awarding $50 to those students with a
poster hanging somewhere inside their room. In addition, every campus
resident received a zipper pull with the normative message on it at
the beginning of the fall 2001 semester. Ever week the "prize team"
randomly stops students on campus and awards $5 to those who display
this pull on something they are carrying. (The award is doubled if a
pair of zipper pulls is worn as matching earrings!)
Robert D. Foss,
University of North Carolina Highway Safety Research Center
CB# 3430, Chapel Hill, NC 27599
University of North Carolina Highway Safety Research Center
CB# 3430, Chapel Hill, NC 27599
"Development and Evaluation of a Comprehensive Program to Reduce Drinking and Impaired Driving Among College Students: Final Report."
Written by Robert Foss, L. Marchetti, and K. Holladay, the full text of the final report of this project published in October 2000 by the National Highway Traffic Safety Administration provides extensive information about the the BAC/social norms study conducted at UNC.
2 Out of 3 .00 BAC Campaign
The web site of the UNC 2 out of 3 .00 BAC campaign. Contents of this site include:
- Details of the
1997 and 1999 breathalyzer study conducted at UNC
- Online Social
Norms Trivia Contest with cash giveaway incentive
- Social Norms
Poster with cash giveaway incentive
of University Students Returning Home at Night." by R.D. Foss,
K.S. Holladay, C.L. Bartley, and L.M. Marchetti. A paper presented at
the proceedings of the 15th International Conference on Alcohol, Drugs,
and Traffic Safety. Borlänge, Sweden: Swedish National Road Administration,
This paper reports the methods and results of the initial, 1997
breathalyzer study conducted at the University of North Carolina. Of
particular interest are the data for actual student BACs by time of
week and the BACs of students by mode of arrival back home.¹
Foss, R. et al. Social norms program reduces measured and self-reported drinking at UNC-CH [University of North Carolina-Chapel Hill]. The Report on Social Norms: Working Paper #14. Little Falls, NJ, PaperClip Communications, 2004.
Research: Blood Alcohol Concentration (BAC) and Breathalyzer Studies
Additional information regarding BAC and breathalyzer studies is available in this section of our web site devoted specifically to research in this area.
¹Note: Much of
the text of this project description was drawn from this paper, with additional information kindly provided by Dr. Robert Foss.
of the information presented on this page were originally prepared by Michael
Haines and Richard Rice and are printed here with their permission.