Drunken Driving,Hit-and-Runs,and BriberyRichard Theroux and John Umbeck

THE PROBLEM of drunken driving and howto control it has been the focus of muchattention in recent years. Public interest

groups have embarked on campaigns to educateus about the risks of drinking and driving. Televi-sion commercials tell us to appoint a "desig-nated driver" if we go out to drink. Many stateshave passed tough new laws against drivingwhile intoxicated (DWI). Yet drunken drivingpersists.

At the core of the problem is the decision-making process of drinking drivers, and the gov-ernment's ability to influence it. In this paper,we present evidence bearing directly on the de-terminants of drunken driving. Using data fromthe state of Ohio, which recently toughened itsdrunken-driving laws, we tested the hypothesisthat drivers respond to the incentives inherent inlegal sanctions, even after they have been drink-ing. The data show that increasing the penaltiesfor DWI had its intended effect: it resulted in lessdrunken driving. At the same time, however, thedata indicate that stiffer penalties induced moredrunken drivers involved in accidents to leavethe scene of the accident. Also, we found someevidence that drunken drivers were more likely

Richard Theroux is an economist with the federalgovernment. John Umbeck is professor of economicsat Purdue University. Peter Meenan of PurdueUniversity provided important assistance in thepreparation of this article.

to offer bribes to avoid arrest under the tougherDWI law.

The evidence appears to confirm our theorythat drinking drivers-even when drunk-re-spond predictably to incentives. This is encour-aging news: it means that carefully structuredregulations, with properly designed incentives,can be effective in reducing drunken driving.

Ohio's DWI Law

Before Ohio toughened its DWI law in 1983, anindividual operating a vehicle with a blood alco-hol concentration of 0.10 percent or more (byweight) was presumed to be under the influenceof alcohol. Since a driver's blood alcohol con-centration merely created a presumption, theprosecutor usually needed additional evidenceto obtain a conviction. This often took the formof testimony from the arresting officer as to thedefendant's performance on the "field test" ofspeech, balance, hand-to-eye coordination, andthe like. By the same token, the defendant couldattempt to refute this evidence. He could, forexample, claim that dental work, a sprained an-kle, or an ear infection was the true cause of thefield test failure and be found not guilty by a jury.

The contestability of this "presumption,"combined with overcrowded court dockets and ashortage of jail cells, put pressure on prosecutorsto plea bargain DWI charges to lesser offenses.

Under this law, Ohio's DWI conviction rate de-clined from 50 percent in 1979 to 39 percent in1982. Over the same period, the percentage oftraffic deaths related to alcohol, initially 36 per-cent, climbed to 42 percent.

A study group on alcohol-impaired drivingappointed by Governor Rhodes in 1981 attrib-uted these trends to the nature of Ohio's DWIlaw and the way it was being enforced. As thestudy group noted, there was a considerableamount of judicial discretion in the way penal-ties were enforced. Mandatory penalties, such asminimum jail sentences for DWI convictions,were sometimes ignored. The likelihood and se-verity of penalties varied not only with the judge(these laws are enforced at the county level) butalso with the circumstances surrounding the ar-rest. Heavier penalties were imposed on thosewho refused to submit to a blood-alcohol con-centration test, tested at higher concentrations,were involved in serious accidents (especiallythose resulting in injury or death), or had priorDWI convictions. Those who did not fall into anyof the above categories were very likely to suc-ceed in plea bargaining the DWI charge to alesser one such as reckless operation of a vehicleor improper vehicle control. Penalties for theseoffenses typically involved fines, and perhaps alicense suspension, but nothing more. Jail sen-tences could be avoided completely.

Effective March 16, 1983, Ohio amended itsDWI law to make driving with a blood alcoholconcentration of 0.10 percent or more a per seviolation, regardless of other evidence. The re-buttable presumption of guilt was removed. As-suming no coincident decrease in the probabilityof arrest, this change in the law increased theexpected cost of DWI. It did so by reducing thelikelihood of a successful plea bargain, and thusincreasing the probability that an arrest wouldresult in a DWI conviction. The increase in costwas greatest for those who were most likely toplea bargain under the old law, typically first of-fenders whose blood alcohol concentration wasno greater than 0.15 percent.

Rational Responses to the New Law

Drinking drivers who wish to avoid the legal pen-alties associated with DWI can respond to thenew law in several ways. One option is to drinkless before driving. Another is to drive less, or todrive more carefully, after drinking. Both of

these choices will reduce erratic driving andthus the likelihood of arrest. These two choices,and their effects on accident rates, have been thefocus of attention by researchers in the field.However, there are two other alternatives avail-able to a drunken driver who is involved in anaccident. He can leave the scene of the accidentbefore the police arrive, or he can bribe theother driver not to report the accident or to de-lay reporting it until he has had time to sober up.Both of these choices have obvious costs associ-ated with them. Nevertheless, higher DWI costsenhance the attractions of these options.

Accidents involving successful hit-and-runs or bribes will either go unreportedor be reported as non-alcohol related.

Our model predicts that drinking driverswill respond to the new law by drinking less,driving less while drunk, leaving the scene moreoften, and bribing more often. Interestingly,each of the four options yields the same predic-tion with regard to reported alcohol-related acci-dents-there should be fewer drivers involved inaccidents reported to have been drinking. Thosewho drink less or drive less will be involved infewer accidents simply by having reduced theirexposure. Accidents involving successful hit-and-runs or bribes will either go unreported or bereported as non-alcohol related.

Testing the Effect of the New Law

The primary data set for the tests we conductedconsists of over 450,000 detailed accident re-ports provided by the Ohio Bureau of Motor Ve-hicles. This includes all reported accidents oc-curring between January 1, 1982 and June 30,1983. The vast majority (about 94 percent) ofthese reports were made by police officers at theaccident scene or later at the police station. Theaccident reports contain only the officer's assess-ment of the extent of alcohol involvement, notthe driver's blood alcohol concentration. Weused these data to classify each driver as drunkor sober.

Drunken Driving. Based on these data, we esti-mated the effect of the new law on the likelihoodthat a driver involved in an accident had been

drinking, controlling for the effects of a numberof other variables. These included the time ofday, the day of week, and the month of the acci-dent, the age and sex of the driver, the conditionof the road at the time of the accident, the type ofpolice filing the report (state, city, or county),aggregated monthly beer and liquor consump-tion, and the local unemployment rate.

We found that under Ohio's new law, theprobability that a driver involved in an accidenthad been drinking fell by about 20 percent, con-trolling for the factors mentioned above. This re-sult is statistically significant and indicates thatthe law affected the level of drinking and drivingas intended. Although 20 percent may not seemlike a dramatic change in behavior, it is impres-sive in light of the fact that the statutory mini-mum penalties were not significantly increasedand the likelihood of conviction was increasedfor only a subset of the drinking and drivingpopulation. We do not know whether the mea-sured change in behavior will persist; other re-searchers have found that the effect of new DWIlaws declines over time.

Hit-And-Runs. Our theory implies that the in-crease in the likelihood of conviction in Ohiowould cause an increase in the number of drink-ing drivers who leave the scene of the accident.Because it is impossible for us to know if a hit-and-run driver had been drinking unless he wasapprehended shortly after the accident, we ex-amined the effect of the law only on solved hit-and-runs. (We defined a hit-and-run driver as adriver reported by the police to have been absentfrom the scene of the accident.) Since approxi-mately one-third of all hit-and-run drivers are ap-prehended, our sample is still quite large.

Under Ohio's tougher DWI law, alcohol-re-lated hit-and-runs increased by about 8 percent.Hit-and-runs in our control group (sober hit-and-runs) fell about 15 percent. Relative to the con-trol group, alcohol-related hit-and-runs thusincreased by about 27 percent.

We also subjected the data to more exactingstatistical tests to determine whether the newlaw had a statistically significant effect on alco-hol-related hit-and-runs. Included in our testswere several other variables that might affect thegains or costs of hit-and-run, such as whether ornot the accident occurred at night or on theweekend. We also included information on theroad conditions at the scene of the accident,whether it was the sheriff or the state police who

investigated, whether the car was disabled, andthe age and sex of the driver. Controlling foreach of these factors, we found that the new lawincreased the number of alcohol-related hit-and-runs relative to sober hit-and-runs. This result isstatistically significant.

Recognizing the possibility of hit-and-runs,our finding of a 20 percent decline in the propor-tion of alcohol-related accidents could be ques-tioned. Since this finding is based on reporteddrunken-driving accidents and no data are avail-able on unsolved alcohol-related hit-and-runs,we cannot isolate the extent to which drunkendrivers are fleeing accident scenes to escape re-porting. However, from our sample of solved hit-and-runs we can get a fairly accurate picture ofthe probable composition of unsolved hit-and-runs. We conclude that the number of unsolvedhit-and-runs involving alcohol, while it undoubt-edly rose, did not rise enough to significantly af-fect the decline in overall drunken driving.

Bribery. Another way a drunken driver canavoid DWI penalties is through bribery. When in-volved in an accident, he may offer compensa-tion to the other party (or to a witness) not toreport the accident. Because most insurancecompanies require that a police report be filedbefore they will pay any accident compensation,bribery is most likely to occur when the acci-dents are minor. In such cases, the damages arebelow the deductible in insurance policies, or atleast low enough to make a cash settlement onthe spot attractive compared to a likely jail termfor DWI.

Unreported accidents are not, of course, inour data set. Another type of bribe is also possi-ble, however. A drunken driver may bribe a wit-ness to delay the accident report until he has hadtime to lower his blood alcohol concentrationbelow the legal limit. This will allow the driver toavoid DWI penalties, without affecting the abilityof either party to seek recovery under their in-surance policies.

Consider the circumstances surrounding abribe. A drinking driver has just been involved insome type of car accident. If no one else is in-volved and there are no witnesses, assuming thecar is still drivable, the driver can leave thescene with impunity. If there is just one witnessor victim, a drunken driver can offer some kindof compensation (bribe) to delay a call to the po-lice. If there are two or more witnesses or vic-tims of the accident, however, a bribe becomes

less feasible. No one witness has an exclusiveright to sell delayed reporting, and each mayhold out for the entire amount the drinkingdriver is willing to offer. Since more than onewitness or victim is typical, we would expect thatonly a small subset of traffic accidents will be"bribable." Bribable accidents are likely to in-volve only one other car with one victim/wit-ness. The accident is likely to be relatively minor(not much noise), to occur at night, and to occur

away from other traffic. In addition, bribable ac-cidents are less likely to involve injuries to eitherparty since delayed reporting could mean seri-ous health problems.

From the accident reports we have avail-able, we can determine whether an accident wasreported at the scene or later at the police sta-tion. Although we do not know how much timemay have elapsed between an accident and itsreport, we used reports filed at the station as aproxy for delay.

Accidents that meet our definition of "brib-able" comprise only a small fraction of the dataset: 384 before the law change and 95 afterwards.Because of its characteristics (minor, late atnight, and remote), this group of accidents ishighly likely to be reported late, even if no brib-ery is occurring. Also because of its characteris-tics, this group of accidents shows a much higherfrequency of alcohol involvement than the dataset as a whole.

Our theory implies that, after the lawchange, alcohol-involved accidents that are brib-able will tend to be reported late as non-alcohol-involved. Before the law change, 50 percent (35out of 70) of late-reported accidents were

reported as alcohol-involved; after the change,31 percent (4 out of 13) were reported as alco-hol-involved. This is a decline of 38 percent-substantially more than the 20 percent decline inoverall alcohol-involvement.

The observed decline could be attributed toseveral effects: bribes not to report alcohol-in-volved accidents; bribes to report these acci-dents late as non-alcohol involved; opportunisticuse of delayed reporting to conceal alcohol in-volvement, with no bribe. The data do not allowus to distinguish these effects. Indeed, the sam-ple size for these accidents is so small that wecannot draw any firm conclusions. The impor-tant point is that bribery is one of the responsesthat is likely to be encouraged when a state raisesthe penalty for drunken driving.

Conclusions

It is impossible to regulate just one aspect of hu-man behavior. Every regulation has secondaryeffects and these effects are often contrary to theregulators' objectives. Economic theory can be apowerful tool in predicting the occurrence ofthese unwanted side effects and in suggestingways in which they can be avoided through acareful structuring of the law.

Our study of the Ohio experience shows thatincreasing the conviction rate for drunken driv-ing can reduce the incidence of alcohol-relatedaccidents but at the cost of more alcohol-relatedhit-and-runs. To reduce the significance of thissecondary effect, legislators could considersimultaneously increasing the penalties for driv-ers who flee the scene of an accident. Indeed, theOhio state legislature is currently considering abill that would raise the hit-and-run penalty tothat for drunken driving. This, however, mightalso make bribery relatively more attractive,which, in turn, might necessitate other changesin the law. By structuring a number of differentpenalties, the economic options of a drinkingdriver can be reduced; with fewer unwanted sideeffects DWI laws can be more effective in reduc-ing the incidence of alcohol-related accidents.

These examples are not intended to be pol-icy suggestions. They are used only to illustratewhat we mean by the "structure" of a regulation,and its importance for individual behavior.There is still much to be learned about variousregulatory structures and the effects they haveon human behavior. -