The benefits of such laws have been demonstrated by a reduction of more than 50% in the number of youth alcohol-related fatalities, from 5,380 in 1982 to 2,206 in 1995 (NHTSA, 1997). A recent national survey of the blood alcohol concentration (BAC) levels of drivers on the road indicated that the proportion of drivers under age 21 who had BACs at the illegal level of .10 or greater declined by almost 90%, from 2.8% to 0.3% between 1986 and 1996 (Voas, et al., 1998).

San Diego Has a Special Problem

San Diego, like other regions in California, has always had an age-21 drinking limit and has been enforcing the state’s zero tolerance law, which is a model for the nation, since its implementation in January 1994 (Martin et al., 1996). San Diego has also had an active, responsible beverage service organization that assists alcohol outlets to avoid serving minors and obviously intoxicated individuals. Oceanside, at the north end of the county, has a major community trial program to reduce alcohol-related trauma, which was funded by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) and has reduced alcohol-related crashes over the 5-year program (Voas, Holder, & Gruenewald, 1997). The special attention given to the drinking-and-driving problem in San Diego County has been very important because the city and its beaches are a major tourist attraction. It is also the center for a number of large Navy and Marine bases, where the enlisted trainees use the county recreational and entertainment facilities. Roadside voluntary breath-test surveys conducted in Oceanside have demonstrated that the number of drinking drivers on the northern county roadways is greater than in a similarly sized city in an agricultural area of northern California (Roeper & Voas, 1998). This provides some evidence that the drinking-and-driving rate is somewhat higher in San Diego, thus requiring greater efforts by law enforcement, health agencies, and the public to combat this problem.

Binge Drinking is a Problem Everywhere

The "Monitoring of the Future" survey of young adults has indicated that drinking by high school students has decreased since 1982, with a slight increase between 1993 and 1995. Throughout that period, a significant portion of students (between 30% and 40%) have reported binge drinking—that is, consuming five or more drinks at a time within the last 2 weeks. Binge drinking is also a significant problem among college students and occurs among some older drinkers as well. Binge drinking, however, can be a special problem for those under age 21 because they are likely to drink away from adult supervision and among their peers, many of whom may encourage excessive consumption.

San Diego has prohibited drinking on beaches and in many parks, where young people congregated to drink. Consequently, areas such as Tijuana, immediately outside the city limits, have become easily available locales for heavy, unsupervised drinking. Since sales to individuals age 18 and older is legal in Mexico, it is attractive to San Diego youth, ages 18 and 21, who cannot legally drink this side of the border. While the number of underaged binge drinkers in San Diego is probably not greatly different from other large cities in the United States, San Diego faces the special problem that young people can cross the border to an area where local enforcement and health agencies cannot deal with the problem.

Easy Access to Alcohol Makes Border Binging a Problem

The health and safety risks presented by young people crossing the border to binge drink has been described on television, in newspaper columns, and, most recently, in an article in Prevention File magazine by James Baker, Director of the Institute of Health Advocacy in San Diego. While the drinking age in Mexico is 18, because of the large number of people descending on Tijuana, this limit is only partially enforced. Television news crews have documented service to females as young as age 13. One bar advertised its "No ID check" policy with a sign on its window.

Aside from the availability of alcohol to individuals considerably younger than those who can legally drink in San Diego, alcohol is very inexpensive in Tijuana. Wednesday night—advertised as "college night"—features 25-cent drinks, and, on all nights, alcohol at the three-dozen-or-so outlets that cater to these young drinkers is less expensive than in San Diego. Signs offering "all you can drink" for $5.00 and "women drink free all night" dramatize this fact. When these young revelers return to San Diego County, many are significantly impaired by alcohol and become victims of drunken brawls or alcohol-related traffic crashes.

In an effort to document the extent of the problem and provide a basis for the San Diego community to act to reduce the traumatic consequences of cross-border binge drinking, the Institute for Health Advocacy, using funds provided by the Alcohol & Drug Services Department, San Diego County Health & Human Services Agency, established a research survey at the border to obtain objective information on the number of U.S. residents returning from Mexico impaired by alcohol.

Monthly Voluntary Surveys

People coming from Mexico cross into San Diego through the San Ysidro port of entry  either on foot or in a motor vehicle. Our survey was designed to cover both modes of entry with teams of interviewers in the building where the pedestrians pass through immigration and customs and on the roadway where vehicles enter the United States (see Photo 1). The survey was limited to U.S. residents age 18 and older entering the United States between 11 PM and 6 AM on one Wednesday, Friday, and Saturday each month. This preliminary report covers the selected weekends from June 1997 through May 1998.

The nighttime survey hours were selected after an initial survey of the times during which young San Diego residents enter Mexico (10 PM to 1 AM) and return to the United States (11 PM to 4 AM). In January 1998, survey times were changed to 12 AM through 6 AM on weekends and 12 AM to 4 AM on Wednesdays. This change was made after an analysis of the data from U.S. Customs. This data indicated that the hours selected may have been missing a substantial portion of the weekend drinking traffic because many crossers apparently do not return to the United States until well after 4 AM. For most estimates, 12 AM to 4 AM are presented.

In addition to Friday and Saturday, one weekday was covered. Wednesday was chosen because it is considered "college night," and many establishments offer drinks at 25 cents each.

Survey Procedures

The surveys follow basic practices established by previous voluntary breath-test survey procedures.

Pedestrians. As pedestrians entered through the INS turnstile, some were randomly chosen and directed to one of the three interviewers who was ready to accept the next interviewee. There, an interviewer explained that the survey is voluntary and asked if the individual will consent to participate. Randomization of selection was maintained by directing the next individual coming through the turnstile to the open interviewer. There were no surveys conducted in September. Approximately 13.2% of those approached refused to provide a breath test or otherwise participate. A total of 3,799 participated during the year.

Drivers. The driver survey was conducted in much the same fashion. The roadway leading from the border was set up so that drivers had to make a set of sharp turns. At the last of these, when they came to a full stop, a San Diego Police Department officer directed them to the side of the road where three interviewers were working. There, an interviewer explained that the survey is voluntary and asked if the individual will consent to participate. Directing the next vehicle to the next open interviewer assured a random sample of drivers. There were no surveys conducted in September. Police scheduling conflicts and rain caused us to miss six evenings of the driver survey. Approximately 10.2% of those directed into the interview bay refused to participate. A total of 2,779 drivers participated.

Interviews and Breath Tests

Once the crosser agreed to participate, a brief interview lasting less than 3 minutes was conducted. The research assistants collected information on age, gender and ethnicity, work status, home zip code, and the purpose of the visit to Mexico. At the end of the interview, respondents were asked to provide a breath sample through a mouthpiece attached to a hand-held BAC test unit. The unit recorded the BACs internally and did not display the result, which was downloaded the next day into a PC.

The interview was entirely confidential. At no time did the research assistant ask the name of the respondent, nor obtain any detailed personal information, such as an address, that would identify the respondent. Further, the BAC was not displayed at the roadside so as not to embarrass the respondent. Obviously impaired individuals (for example, those who were carried across the border unconscious, or were vomiting, or otherwise indicated that they were in distress or likely to be heavily impaired) were taken into custody by the San Diego police or the California Highway Patrol (CHP). These individuals were not interviewed, so the data summarized below does not include individuals who were clearly too impaired to participate. The number of such individuals, however, was small relative to the total number crossing the border and the number who had been drinking heavily.

July 1997 Exclusion

Data from the July survey are excluded from most of the analyses presented here. On the first weekend of July, Mexico held national elections. Concurrently, Mexico prohibited all sale of alcohol. This resulted in a remarkable change in the border crossing behaviors of U.S. residents. We discuss the effects of the July weekend prohibition separately.

U.S. Customs Census

As vehicles and pedestrians cross into the United States, they are counted by the U.S. Customs. Pedestrians are counted through a turnstile counter, and vehicles are counted through recordation of license plate numbers. These counts were compiled into hourly totals and provided to us for this project. We used the hourly counts to indicate the traffic flow during peak drinking times and to properly weight our survey sample of pedestrians and drivers.

Photo 1. Locations of surveys at the San Diego/Tijuana Border

(click on image to view a larger photo)

Numbers of Pedestrians and Vehicles: 11 PM to 6 AM

Figure 1 shows the average number of pedestrians and the number of vehicles that were entering the United States on Wednesday, Friday, and Saturday nights. These data were taken from INS records. As can be seen, the number of both pedestrians and vehicles is clearly higher on weekend evenings than on Wednesday evenings. During the hours from 11 PM to 6 AM, more than 10,000 individuals crossed the border. Thus, a large staff of INS and Customs officials was needed to handle the traffic load. Further, this placed significant stress on the two to three San Diego Police Department officers handling the pedestrian flow and the limited number of CHP officers responsible for the entering motorists.

Figure 1.  Average number of pedestrians crossing into San Diego

(click on image for a larger view)

Ethnic Differences

The ebb and flow of crossings per hour differ for pedestrians and drivers, as can be seen clearly in hourly counts presented previously. This may stem from the differing functions the two modes of crossing offer. Between 11 PM and 6 AM, the peak times for drivers are between 11 PM and 12 AM and, then again, (especially for Wednesdays) between 5AM and 6 AM. This probably reflects the use of the vehicle crossing point by those who commute to work in San Diego. Pedestrians crossing between 11 PM and 6 AM, on the other hand, are far more likely to be young U.S. residents coming home after the bars and nightclubs in Tijuana begin closing.

This seeming difference is confirmed through our survey of northbound crossers. The characteristics of pedestrians and drivers are quite different, as shown in Figure 2. The majority of the pedestrians are White. For drivers, however, more than three-out-of-four are Hispanic, and less than 17% are White. The young U.S. drinkers, who are apparently less comfortable with driving into Mexico, are more likely to drive to the border, park their vehicles, and walk across.

Figure 2.
Ethnicity of drivers and pedestrians crossing into San Diego between 12 AM and 4 AM

(click on image for a larger view)

Age of Drivers and Pedestrians

Figure 3 gives the age distribution of pedestrians and drivers. The pedestrians, with more than 40% under age 21, are clearly younger than the drivers, about 60% of whom were over age 26.

Figure 3.
Age of drivers and pedestrians crossing into San Diego between 12 AM and 4 AM

(click on image for a larger view)

Gender of Drivers and Pedestrians

Males are, by far, the majority of the pedestrians and drivers. However, males are most over-represented among the older age groups. Figure 4 shows a clear tendency for more females to be among the younger age groups for both drivers and pedestrians. For the 18-to-20-age group, about 40% of the border crossers are female, whereas for older groups, this percentage is closer to 20%.

The similarity between the number of female pedestrians and the number of female drivers interviewed in the 18-to-20-age group is interesting. Past traditions would suggest that males would be more likely to be driving during nighttime hours. However, for this age group, the proportion of female drivers is approximately the same as the proportion among the pedestrians. The proportion of males and females among the pedestrians represent all crossers, while the proportion of males and females among the drivers may not represent all crossers. This occurs with drivers crossing the border because the gender of passengers was not recorded.

Figure 4.
Gender of pedestrians and drivers by age crossing into San Diego between 12 AM and 4 AM

(click on image for a larger view)

Vocational Status Differences

Another difference between pedestrians and drivers is shown in Figure 5, which gives the work status of those crossing the border into the United States between 12 AM and 4 AM. As can be seen, most drivers stated that they are employed, and only a small portion are in the military or attending a university. In contrast, those employed are only about two-fifths of the pedestrian group. Almost one-half of the pedestrian group comes from either the military or the universities in the San Diego area. This again fits the pattern of the motorists being principally Hispanic who are visiting relatives or friends, or commuting to their homes or jobs, whereas the pedestrians are principally White and from military bases and local universities.

Figure 5.
Vocational/organizational affiliations of pedestrians and drivers crossing
into San Diego between 12 AM and 4 AM

(click on image for a larger view)

BACs of Pedestrians and Drivers

As shown is Figure 6, there is a strong contrast in the measured BAC of drivers and pedestrians. Three out of four drivers had not been drinking, while the majority of those who had been drinking were below the .08 legal BAC limit in California. In contrast, more than half of the pedestrians had been drinking, and nearly half of those who had been drinking were greater than the .08 BAC limit. The BAC levels of the drivers are consistent with the assumption that they had probably been visiting friends or family rather than drinking in Tijuana establishments. Therefore, they were less likely to have been drinking. It is also probable that the knowledge of the .08 BAC limit in California and the active enforcement of this limit by the San Diego police and the CHP helped ensure that drivers would be at lower BACs than pedestrians.

Figure 6.
BACs of pedestrians and drivers crossing into San Diego between 12 AM and 4 AM compared to nighttime roadside survey participants in Oceanside, California

(click on image for a larger view)

However, many of the pedestrians had parked their cars at the border. Others who used the trolley or other public transportation to the City of San Diego may still have driven from the trolley or bus terminal to their homes. Pedestrians tend to travel into Tijuana and return in small groups, so it is possible that many of those with higher BACs were passengers rather than drivers of vehicles. While some information was obtained on whether an individual was driving, it was not possible to determine whether those who claimed to be passengers were in a group where the driver had a lower BAC.

The third pie chart (Figure 6) is a comparison with a roadside survey conducted over 4½ years (1991-1996) at the northern end of the county. In Oceanside, weekend drivers were stopped between 10 PM and 2 AM and were asked to provide a breath test. Note that the percentage of drivers with BACs greater than .08 at the border (8.3%) is more than twice that of the Oceanside drivers, while the percentage for pedestrians at the border is almost ten times as high (30.9% vs. 3.2%). The mean BAC for pedestrians and drivers by age group is shown in Figure 7.

Figure 7.
Mean BAC by age and day of week for pedestrians and drivers crossing
into San Diego between 12 AM and 4 AM

(click on image for a larger view)

Figure 8 provides information on the relationship between the age and the probability of being over the California DUI limit of .08 BAC. It is noteworthy, however, that among the underage group (ages18 to 20), one in four of the pedestrians were over the adult legal limit of .08.

Figure 8.
Age and probability of being more than the .08 legal limit in California

(click on image for a larger view)

As shown in Figure 9, the 18- to 20-age group represents the largest number with BACs more than .08. These young border crossers also represent the largest portion of the pedestrian sample, which is not the case among drivers.

Figure 9.
Proportion of all drivers and pedestrians with BACs
at or greater than .08 falling into each age group

(click on image for a larger view)

The proportion of pedestrians and drivers with BACs greater than the .08, the legal limit in California, is shown in Figure 10 by vocation. The "other" group included homemakers as well as unemployed and retired respondents.

Figure 10.
Proportion of pedestrians and drivers at BACs greater than .08 by vocational status

(click on image for a larger view)

Number of High BAC Pedestrians

Figure 13 provides an estimate of the total number of individuals having a BAC of more than .08 returning to San Diego on Wednesday, Friday, and Saturday nights. The data are broken down into vocational associations. As can be seen, if a method were to be developed to interdict the return of individuals whose BACs were more than the legal limit, the number of cases to be handled on any given night would be very large. Estimates from the surveys on Wednesdays (between 12 AM and 4 AM) indicate that almost 500 pedestrians were legally impaired based on a BAC of .08 or greater. The number was even larger for the weekend. On Friday and Saturday nights, more than 800 pedestrians were impaired. If an effort were made to screen pedestrians returning to the United States, and those having BACs greater than the limit were taken into protective custody pending arrangements for safe transport home, a large holding facility would be required. Such a facility would need an adequate staff of security and medical technicians or nursing personnel. It would also require a large contingent of volunteers to arrange for transportation for individuals who were not accompanied by sober drivers.

Figure 13.
Estimated total number of pedestrians crossing into San Diego between 12 AM and 4 AM with BACs greater than the .08 legal limit by vocational category

(click on image for a larger view)

Estimates of drivers and pedestrians planning to drive home in violation of an alcohol-related law indicate that it would take a significant enforcement effort to detect and process all violators. Drivers with BACs at or greater than .08 are in violation of a per se DUI law in California. Additionally, drivers under age 21 with alcohol in their system (usually defined as a BAC at or greater than .02) are also in violation of California’s "zero tolerance" law. Figure 14 shows the number of drivers and pedestrians planning to drive who will be either violating the zero tolerance law (BAC between .02 and .08, plus under age 21) or the .08 per se law.

Figure 14.
Alcohol driving violations by those leaving the border area between 12 AM and 4 AM

(click on image for a larger view)

Most of those entering Mexico to drink and patronize the Tijuana clubs do so in groups. This is important to understand because the members of a group may play an important role either in encouraging individuals to drink more or in limiting their consumption. A group can provide a means for using a designated driver, but a group can also put pressure on members to drink more.

The effect of the drinking group on the individual’s alcohol consumption was investigated by adding another survey to the northbound program for returnees. When the interviewers had approached individuals earlier in the evening when they entered Tijuana, whole groups were asked to fill out a brief questionnaire, which normally required 5 to 10 minutes, and provide a breath test. In addition, each anonymous respondent was given an identification number on a small band that could be worn around the wrist or in a belt loop. They were asked to identify themselves to the northbound interview team at the end of the evening when they returned from Tijuana. At that time, they took part in the regular northbound interview, including providing a breath test. To encourage their participation in this dual-interview program, each member of the group was offered a $10 postal money order, which they could pick up after the northbound interview.

Using this procedure, we could determine the distribution of group sizes entering Mexico to drink. This is shown in Figure 15. As can be seen, the group size averaged three to four people, and more than two-thirds of the groups were more than two.

Figure 15.
Number and size of pedestrian groups in our sample of young people crossing into Mexico between 10 PM and 1 AM

(click on image for a larger view)

We could also determine how the group members reached the border from San Diego. As can be seen in Figure 16, 89.4% of these pedestrians entering Mexico had reached the border by vehicle. Only a fraction arrived through public transport or by walking from a nearby neighborhood. Figure 17 shows that there appeared to be a relationship between the method used to get to the border and the probability of returning with a BAC greater than the California limit of .08.

Figure 16.
Method by which southbound pedestrians (10 PM to 1 AM) reached the border from San Diego

(click on image for a larger view)

Figure 17.
Proportion of returning pedestrians with BACs grater than .08 based on
the transportation method they used to reach the border

(click on image for a larger view)

Most of those heading to Tijuana late at night on weekends and Wednesdays were at least partially motivated by the alcohol. Going into Tijuana, more than 70% said they planned to drink. Almost half reported that they planned to get either "a little" or "very" drunk. Figure 18 shows the percentage of men and women who planned to drink.

Figure 18.
Drinking plans of pedestrians heading into Mexico between 10:00 PM and 1:00 AM

(click on image for a larger view)

Figure 19 shows the clear relationship between drinking plans and returning BACs.

Figure 19. Median BAC of pedestrians returning to San Diego based on
their reported drinking intentions when headed into Tijuana

(click on image for a larger view)

We have included in the survey a number of questions designed to make the respondents compare features of the Tijuana and San Diego night scenes. In this way, we can understand what motivates them to expend additional effort and time to travel to Tijuana. Of course, those under age 21 are clearly motivated by the lower drinking age in Tijuana. However, Figure 20 shows that a several other features also seems to motivate youth to drink in Tijuana, including the price and the feeling that one can more easily get "drunk" in Tijuana. These features seem to outweigh the negative features such as poor safety.

Figure 20. How pedestrians under 21 heading into Tijuana rate
TJ clubs in comparison to San Diego clubs

(click on image for a larger view)

References

Hingson, R., Heeren, T., & Winter, M. (1996). Lowering state legal blood alcohol limits to 0.08 percent: The effect on fatal motor vehicle crashes. American Journal of Public Health, 86, 1297–1299.

Martin, S., Grube, J., Voas, R. B., Baker, J., & Hingson, R. (1996, November Supplement). Zero tolerance laws: Effective public policy? In J. D. Beard (Ed.) Alcoholism: Clinical and Experimental Research. Reports of the Joint Scientific Meeting of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism. (Vol. 20, pp. 147A–150A). Baltimore, MD: Williams & Wilkins.

National Highway Traffic Safety Administration (NHTSA). (1997). National automotive sampling system: Crashworthiness data system 1992–1994. Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration.

Roeper P., Voas R.B. (1998) Alcohol consumption measured at roadside surveys and variations in traffic injury crashes. Accident Analysis & Prevention, 30(4):409–416.

Voas, R. B., Holder, H. D., & Gruenewald, P. J. (1997). The effect of drinking and driving interventions on alcohol-involved traffic crashes within a comprehensive community trial. Addiction, 92(Supplement 2), S221–S236.

Voas, R. B., Wells, J., Lestina, D., Williams, A., & Greene, M. (1998). Drinking and driving in the United States: The 1996 national roadside survey. Accident Analysis and Prevention, 2, 267–275.