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Differential Effects of Deterrence - What Can be Learned from Raising a BAC Limit

Hans-Peter Krüger

Center for Traffic Sciences, University of Wuerzburg, Röntgenring 11, D-97070 Würzburg, Germany


With the reunification of Germany, the eastern part of Germany (the former GDR) raised the legal BAC limit from 0.0% to 0.08%. To study the effects of this unusual change in legislation, an extended roadside survey was conducted in two contiguous border states that were formerly in East and West Germany. Based on a representative random sampling plan, the survey was conducted in three waves: the first, 2 months before the legal change on January 1, 1993; the second, 5 months thereafter; and the third, in June 1994. In all, more than 21,000 drivers participated, with more than 95% agreeing to a breath test. During daytime hours, only 5% of all drivers were found to be alcohol positive (BAC > 0.0%), approximately 0.5% of whom had BAC values greater than 0.08%. For the night time drivers, 15% were found to have a BAC greater than 0.0% and 1.5% a BAC greater than 0.08%. Comparison among the different waves showed that the change in legislation was not a cue for the general driving population to alter its drink-driving behaviour. On the other hand, it became evident that young drivers and hard-core drinkers reacted markedly to the change. In East Germany, the pathological result was that the percentage of intoxicated drivers increased as the drivers' ages decreased. In addition, the average BAC of East German drivers involved in accidents increased significantly after the reunification. Thus, "novices" in drinking and driving and "experts" in heavy drinking were identified as vulnerable subgroups which react very sensitively to perceived changes in the legal definition of DUI.


The BRD, and now Germany (throughout the text, the acronyms BRD and DDR are used to identify West and East Germany, respectively, before reunification, whereas the term Germany signifies the unified country) has a multi-tier alcohol legislation. First, there is a per se blood alcohol concentration (BAC) limit of 0.11% (considered "absolutely unfit to drive") which, according to the penal code, characterizes violators as offenders. At lower measurements, the prosecution depends on the consequences. In cases when no accident has occured, a second (administrative) per se limit of 0.08% exists. Violators are prosecuted by license suspension and fines, but are not considered as offenders legally. Persons at BAC levels lower than 0.08% are not prosecuted, although in the case of an accident, a presumptive regulation allows for punishment according to the penal code if the intoxication level (0.03-0.11%) is presumed to be responsible for the accident. This range is characterized as "relatively unfit to drive" (Figure 1).

Figure 1
The Change, Relative to BAC in the Legal Situation in the Eastern Part of Germany

The right side shows the situation in the former West Germany (BRD) which, as of January 1, 1993, also became the legal situation in the former East Germany (DDR). The middle part of the figure shows the interim regulation. PC = Penal Code; AL = Administrative Law.

With regard to alcohol-related accidents, the alcohol legislation of the DDR was nearly the same as in the BRD. At BAC levels lower than 0.02%, alcohol was not presumed to be a causal factor in the accident, whereas persons at higher intoxication levels were prosecuted by the Penal Code. Persons at intoxication levels greater than 0.10% were considered "absolutely unfit to drive". Because a zero BAC limit was generally in force, each person at an intoxication level higher than 0.02% was prosecuted by the police (a solution comparable to the BRD's administrative one). When no accident occured, the DDR law had no per se BAC limit comparable to the 0.11% limit in the BRD. Even persons at high intoxication levels did not qualify as offenders.

Therefore, the real difference between the BRD and the DDR was in the prosecution of persons with BAC levels ranging from 0.02% to 0.08% in cases when no accident occured. In addition, the informal nonprosecution of persons at BACs lower than 0.02% in the DDR was slightly different compared with the BRD's solution of considering BACs up to 0.03% as legal. This difference, clearly not very drastic, became part of the public and political discussion and was reduced to the question whether alcohol should be allowed in traffic at all. Even more drastic, oppposing views were represented ideologically as "the Western ideal of individual self-responsibility" versus "Eastern school-mastering" or "Western permissiveness" versus "Eastern common sense". Thus, the harshness of the public discussion was in no way proportional to the actual difference between the two legislations.

Even more complicated was the time course of the reunification and its legal consequences. The DDR law was in full effect until the fall of the Berlin Wall in November 1989. Beginning July 1, 1990, the West German DM currency was introduced in the DDR, a step which was understood by the people as the real reunification and as the actual end of the DDR (called the "Wende", meaning "the turn"). The reunification was legally an accession of the DDR into the BRD. This "Beitritt" ("joining"), which involved adoption of the whole West German legal system, happened on October 3, 1990, from which date the Penal Code of the BRD was also enacted in the former DDR. The consequence was that, in the case of accidents, the BRD alcohol legislation was applied in Germany. By an exemption in the Treaty of Unity, the administrative regulations with regard to driving under the influence of alcohol (DUI) remained unchanged in the two parts of the country. The Treaty of Unity provided that within 2 years a new common regulation would be established. If not, from January 1, 1993, the BRD's administrative DUI regulation would be valid in the unified Germany. In the time from the "Beitritt" to January 1, 1993, the states in the former DDR partially adapted their regulations to the law of the BRD. Still, in all cases, persons at BACs between 0.05% and 0.08% were prosecuted in the former DDR but not in the former BRD. Beginning January 1, 1993, the BRD's regulation became valid in all parts of Germany because none of the parliamentary attempts to change the BRD law were successful.


The prevalence of DUI before the reunification was not documented in either the DDR or in the BRD by roadside surveys. Thus, only accident statistics can be used. Unfortunately, the two statistical systems differed in important features, hindering a direct comparison. In addition, after the reunification in 1990, the BRD's statistical system was introduced in the DDR with the consequence that the DDR data cannot be used for a before and after comparison. Even worse is that in 1990-1991 the BRD's system was not fully understood and applied in the DDR. Therefore, the 1990 data cannot be trusted. To make the situation even more complicated, during the years between 1989 and 1991 car ownership increased, resulting in more than double the number of cars, an incredible increase in traffic density, and a desperate situation for the police with a dramatic decrease in enforcement. Comparison of the accident statistics from 1989 to 1991 within the former DDR and between the DDR and the BRD, therefore, is nearly impossible and is full of implications which cannot be proved.

To comprehend the effects of a law raising the BAC limit - as was the case in the DDR in 1993 - we conducted an extended roadside survey in two comparable regions. The eastern region was located in the middle of the state of Thüringen (DDR) and the western region was north of Bavaria (Unterfranken, BRD). Both have approximately 3 millions of inhabitants. Three waves were conducted: the first in November/December 1992, the second in May/June 1993, and the third in May/June 1994 (A detailed description of the study is given in Krüger et al. in this same volume).

In Thüringen, 11,571 drivers took part in the survey and in Unterfranken, 11,447 drivers. The drivers were stopped and checked by the police following a representative sampling plan. At a separate checkpoint, the drivers were interviewed and asked to supply a breath sample. In Thüringen, 96.7%, and in Unterfranken, 94.8% agreed to the breath test; 98.9% in Thüringen and 92.8% in Unterfranken took part in the interview.


The Official Accident Statistic

Despite their shortcomings (mentioned above), official accident statistics are the only source for describing the development of alcohol-related accidents (Figure 2).

Figure 2
Casuality-Involved Accidents and Proportions of Alcohol-Related Accidents in West and East Germany

On the left, the progress of casuality-involved accidents in the East (grey line) and West (black line) is shown. Data are referred to the number of accidents in 1975 as 100%. The numbers in the figure give the percentages for the East in the years 1989-1994. On the right side, the proportion of alcohol-related accidents is shown for the East (grey line) and West (black line). The numbers show the proportions for the East starting in 1989.

The left side shows the dramatic increase in casuality-involved accidents in Thüringen after the Wende. The percentages for Unterfranken declined slowly but continuously (comparable to the development in the BRD). In the DDR, the rate of alcohol-related accidents (right side) decreased until 1989 to 9.7%. In 1990, this percentage went up to 11.6%, reached ist maximum in 1993 with 16.3%, and started to decline in 1994.

Thus, the 1993 change in legislation seems to have only a small, short-term effect on accidents when compared with the year before and thereafter. The 1993 increase in the 1.1% proportion was nearly totally compensated for by the 1994 decrease. If the data are trustworthy and comparable, the real change in the accident situation happened in 1990, after the Wende, when the old DDR law was still valid. A dramatic increase was seen in the absolute number of alcohol-related accidents.

The Results of the Roadside Survey

Table 1 gives the results of the three waves of the German Roadside Survey (GRSS): 1992 (before), 1993 (three months after the change), and 1994 (15 months after the change).

Table 1
Percentages of DUI Drivers for the Three Waves (1992-1994) in East and West Germany

    Thueringen (East) Unterfranken (West)
    92 93 94 92 93 94
overall n 2810 3798 4491 2806 3028 3231
% BAC - 0.08 8.11 8.00 6.90 8.66 7.76 9.00
% BAC 0.08+ 0.93 1.47 0.94 0.82 1.22 0.84
male n 2293 3016 3532 1997 2174 2287
% BAC - 0.08 8.68 9.12 7.81 10.12 8.97 10.41
% BAC 0.08+ 1.09 1.76 1.10 1.15 1.61 1.09
female n 517 782 959 809 854 944
% BAC - 0.08 5.61 3.71 3.55 5.07 4.68 5.61
% BAC 0.08+ 0.19 0.26 0.31 0 0.23 0.32
18 - 24 n 799 1040 1178 909 888 869
% BAC - 0.08 10.89 10.19 9.00 8.47 6.19 7.13
% BAC 0.08+ 0.88 1.54 1.61 0.44 0.34 0.35
25 - 49 n 1564 2128 2488 1508 1678 1809
% BAC - 0.08 7.67 7.71 6.79 9.28 8.34 9.40
% BAC 0.08+ 1.15 1.60 0.72 1.19 1.43 1.27
50 and older n 446 630 825 389 462 553
% BAC - 0.08 4.48 5.24 4.48 6.68 8.87 10.67
% BAC 0.08+ 0.45 0.95 0.61 0.26 2.16 0.36
day n 1364 1844 2180 1362 1470 1568
% BAC - 0.08 3.59 3.42 2.71 4.11 3.27 4.78
% BAC 0.08+ 0.22 0.60 0.37 0.22 0.75 0.38
night n 1446 1954 2311 1444 1558 1663
% BAC - 0.08 12.31 12.33 10.82 12.95 12.00 12.93
% BAC 0.08+ 1.52 2.35 1.51 1.39 1.67 1.26
workday n 1300 1757 2077 1298 1401 1495
% BAC - 0.08 5.31 6.55 5.20 6.16 5.28 6.49
% BAC 0.08+ 0.46 1.20 0.53 0.46 0.57 0.80
weekend n 1510 2041 2414 1508 1627 1736
% BAC - 0.08 10.46 9.26 8.37 10.81 9.90 11.18
% BAC 0.08+ 1.32 1.76 1.28 1.13 1.66 0.86
The global result is stratified by gender, age, time of the day, and workday vs. weekend. For each subgroup, the number (n) of observations is given, followed by the percentage of drivers with BACs up to 0.08% and those with BACs of 0.08% and higher. The data are unweighted.

For the evaluation of the effect of raising the BAC limit in the East, two comparisons are important: (1) the time course of the percentages of drivers with low and high BACs in the East where the legal BAC limit changed, and (2) the comparison of the two time courses of the East and the West, which is intended to control for confounding variables. Therefore, the differences in the percentages of Table 1 were evaluated by Chi-square statistics. The resulting probabilities were classified into "significant" if p < .05 and "tendency" (p < .25) (Table 2).

Table 2
Result of the Testing for Differences by Chi-square

  East West West vs East
  92 vs 93 93 vs 94 92 vs 93 93 vs 94 92 93 94
below 0.08%
overall . - - - + . . + +
male . - - - + + . + +
female - . . . . . + +
18-24 . . - . - - - -
25-49 . - . . + . + +
50 and older . . . . + + + + +
0.08% and higher
overall + + - - + - . . .
male + + - - + - . . .
female . . . . . . .
18-24 + . . . . - - - -
25-49 + - - . . . . +
50 and older + . + + - - . + .
The changes were signed according to the direction of the difference either with a doubled sign if significant (p < .05), or by a single sign if a tendency was found (p < .25). A plus in the last three columns means that the proportion in the West was higher than in the East. Accordingly, a plus in the first four columns means that the proportion in the later year was higher than in the year before.

In the high BAC class in the East, a significant increase in DUI driving in 1993 is found in the overall percentages as well as within the subgroup of males. This increase was compensated in 1994 by a significant decrease with exception of the young drivers. However, this development is not necessary an effect of raising the BAC limit because a comparable development is found in the West, where the overall percentage as well as the one for males and especially for older drivers increased in 1993, too, and decreased in 1994. Although the increase in the East in 1993 is stronger and significant for the overall percentage and for males, the comparisons of East and West per year show hardly any significant differences. In 1992, there was no difference either in the overall percentages or in those of the subgroups. The same holds true for the years 1993 und 1994, with the exception of the younger drivers. Whereas in the West these young drivers show fewer and fewer trips with high BAC (although not reaching significance), this percentage increases continuously in the East. Thus, for the drivers with high BAC, the assimiliation between East and West was finished in 1992. Most likely, there never was a difference for this group of drivers even in the old DDR.

The effects within the low BAC group were quite different. The legal change in 1993 in the East produced no effects, whereas 1994 brought a significant decrease of DUI driving. This should not be considered a general development (as for the high BACs) because, at the same time in the West, a tendency towards more frequent driving with low BACs can be observed (in 1994, for nearly all subgroups more drivers with alcohol are found in the West). The decrease in 1994 of driving with BACs up to 0.08% in the East is most prominent for the males. Again, as with those in the higher BAC class, these young drivers in the East drive more often after consuming alcohol than their Western peers.

In sum, this analysis revealed two subgroups of drivers vulnerable to the raising of the BAC limit. The first subgroup consists of drivers with BACs of 0.08% and higher, who show a slightly stronger increase in 1993 than the respective drivers in the West. However, in 1994 the situation in East and West was again nearly the same. Thus, the changes in this subgroup seem to be temporary. The second subgroup consists of young drivers, who continue to drive more often with alcohol than their Western peers. In this subgroup, the changes threaten to have more long-term effects.

In addition, the basic similarities and differences between the East and West have not changed from 1992 to 1994. The East in the days of the former DDR was characterized by a lower percentage of people driving with low BACs. The difference between the East and the West was smaller in the years after the Wende (in 1989), but increased again in 1993-94. For the high BAC group, the situation in East and West was nearly the same in the last years of the DDR and remains so up to 1994.


Assuming (1) that driving with a low BAC is mostly a characteristic of moderate drinkers, and (2) driving with BACs over the legal limit is an indicator of heavy drinking, the change in legislation was only a slight and transitory cue for the moderate drinkers to alter their drink-driving behavior. Evidently, long term mental sets and convictions regulate the decision whether to drink and drive. There may be a slight tendency to "test the limits" when the BAC limit is raised, but not over the long term. This interpretation is supported by the finding that the older the driver, the less likely he or she was to be alcohol positive. In the same way, women in the East drive less and less frequently at low alcohol levels. Thus, the moderate drinker behaves conservatively and makes decisions about drinking and driving according to inner mental standards.

The radical groups, that are very sensitive to changes in the external drunk driving situation, are the younger drivers and heavy drinkers. For heavy drinkers (drivers with a BAC of 0.08% and more), a similar development was observed in the East and in the West. Trips undertaken by drivers with BACs above the legal limit showed an increase of about 50% in 1993 in the East and in the West. However, this increase was stronger in the East. This development was transitory and followed by a decrease in 1994. In none of the years a clear difference was found between East and West, with the exception of, again, young drivers. This stability in drunk driving frequency is overshadowed by a finding from accident statistics. For BACs below 0.20%, less accident drivers are found in the East than in the West. For BACs above 0.20%, more drivers are found in the East. This means that drunk drivers in the East are more heavily intoxicated than in the West. If the data of the former DDR are to be trusted, the average BAC of accident drivers was 0.17%, exactly the same value as in the former BRD. Because the average BAC in the western states of Germany is still 0.17%, these significant differences between East and West in the accident BACs reflect a new development. The former hard-core drinkers of the DDR now drink even more. Thus, these hard-core drinkers form the second subgroup who was also affected by the change in the DUI legislation, although this change only concerned the BAC range between 0.05 and 0.08%.

The most alarming development comes from the young drivers. Lacking the stabilizing mental sets of the older drivers concerning drunk driving, they react strongly to the perceived liberalisation of alcohol in traffic. The situation is pathological: the younger a driver in the East, the more probable it is that he will drive under the influcence of alcohol. For the low BAC class, this development seems to slow down (in 1992 10.9% of all trips, in 1994 9.0%), but was stronger in the high BAC class (1992 0.9% trips, 1994 1.6%). Considering that, in the West, DUI decreases continuously for young drivers, the East German traffic is threatened by a growing group of young hard-core drinkers.

Therefore, it seems that hard-core drinkers, especially when they are young, are a vulnerable subpopulation that is very sensitive to changes in the public evaluation of DUI. More important than the formal legal situation is the way it is perceived by the driving population. This is proved in that the changes in alcohol-related accidents happened in 1990 when the legal situation had not yet changed. Thus, the changes in the behavior of subpopulations preceded the changes in the legal situation. Drunk driving does not wait until a new law is in effect. It reacts instantly on perceived changes in the public evaluation of DUI.

In addition, the legal changes do not affect the whole population. Most drivers decide about drinking and driving depending on their inner mental standards, which can only be altered over a long time. But the young driver, as a "novice" in drinking and driving, and the "expert" in heavy drinking react more to the public re-evaluation of drunk driving which is reflected by the raising of the BAC limit. Both groups have the highest accident risks (see also Krüger, Kazenwadel & Vollrath, in this same volume). Therefore, even small changes in the number of DUI trips may have led to the dramatic effects observed in the development of alcohol-related accidents in the East. Thus, the concept of a general deterrence strategy should be expanded to a concept of differential deterrences, with each one specific for different subgroups of the driving population.


Krüger, H.P., Kazenwadel, J. & Vollrath, M. Grand Rapids effects revisited: Accidents, alcohol and risk. Proceedings of the 13th International Conference on Alcohol, Drugs and Traffic Safety (in this volume).