Introduction Following Stricter Drunk Driving Regulations Chad D Cotti University of Connecticut Project Co-Authors: Nathan Tefft, University of Washington and Scott Adams, University of Wisconsin - Milwaukee The current maximum legal blood alcohol content (BAC) in all 50 states is 0.08, and the NTSB recently proposed that all states move to a 0.05. The 0.05 threshold is a common limit across the globe, and the NTSB predicts such a move would save many lives. Given the high cost of drunk driving conviction; economic theory would suggest that drunk drivers will undertake behaviors to avoid detection (e.g. following driving laws more closely) Stricter legal blood BAC thresholds will increase the likelihood of being detected as a drunk driver, and hence should increase avoidance behaviors. Introduction We speculate that drunk drivers will adjust their seatbelt use in light of BAC threshold changes in cases where local seatbelt laws are primarily enforced. Hypothesize that stricter BAC laws in conjunction with primary seatbelt enforcement will increased belt use and reduced number of fatal accidents among intoxicated drivers. Objective:Establish whether drunk drivers are more likely to use their seatbelts if the probability of detection from law enforcement increases Background: Seatbelt Laws The first meaningful legislation pertaining to seatbelts in the U.S. was passed in 1961 in the state of Wisconsin. All cars were required to be equipped with front-seat restraints but no mandates on usage were specified. Federal legislation followed in 1968, but as with the Wisconsin legislation, no requirements on usage were established. The first law that mandated that seatbelts actually be used was passed in the state of New York in 1984. Many states followed with similar legislation, and currently only New Hampshire does not require seatbelt usage for adults.
Background: Seatbelt Laws Typically, mandates come in two forms and apply to everyone in the front seat: Secondary enforcement: Driver is subject to a fine for not wearing a belt if they are pulled over for another infraction. Primary enforcement: Driver is fined for driving or riding without a seatbelt independent of any other offense. Lots of variability across locations and time in these laws. State Any Belt Law: Initial effective Belt Law: Primary Enforcement AL 7/18/1991 12/09/99 AK 9/12/1990 05/01/06 AR 7/15/1991 06/30/09 CA 1/1/1986 01/01/93 CT 1/1/1986 01/01/86 DE 1/1/1992 06/30/03 DC 12/12/1985 10/01/97 FL 7/1/1986 6/30/09 GA 9/1/1988 07/01/96 HI 12/16/1985 12/16/85 IL 1/1/1988 07/03/03 IN 7/1/1987 07/01/98 IA 7/1/1986 07/01/86 KS 7/1/1986 6/10/10 KY 7/15/1994 07/20/06 LA 7/1/1986 09/01/95 ME 12/26/1995 09/20/07 MD 7/1/1986 10/01/97 MI 7/1/1985 04/01/00 MN 8/1/1986 06/09/09 MS 7/1/1994 05/27/06 NJ 3/1/1985 05/01/00 NM 1/1/1986 01/01/86 NY 12/1/1984 12/01/84 NC 10/1/1985 12/01/06 OK 2/1/1987 11/01/97 OR 12/7/1990 12/07/90 RI 6/18/1991 6/30/11 SC 7/1/1989 12/09/05 TN 4/21/1986 07/01/04 TX 9/1/1985 09/01/85 WA 6/11/1986 07/01/02 WV 9/1/1993 07/1/2013 WI 12/1/1987 06/30/09 Do Seatbelt Laws work? First set of studies used mass implementation during 1980s and early 1990s. Meta-analysis in American Journal of Preventive Medicine (Dinh-Zarr 2001) Overall effects of seatbelt legislation Seatbelt use Fatal injuries Nonfatal injuries 13% - 19% increase 2% - 18% reduction 15% reduction - 11% increase Incremental effectiveness of primarily enforced laws (over secondary) Seatbelt use Fatal injuries 1% - 22% increase 3% - 14% decrease Background: On BAC legislation Legislation against driving while intoxicated in the U.S. has generally always been prohibited if not actually enforced. 1960s saw many states set 0.15 BAC as the legal limit; How does one achieve 0.15 BAC? 190 lb Male: 8 drinks in 1 hour;10 drinks in 4 hours By 1980s, many states moved to 0.10 5.5 drinks in 1 hour; 8 drinks in 4 hours Today every US state is subject to 0.08 First state was Oregon in 1983; last was MN in 2005 4.5 drinks in 1 hour; 5.5 drinks in 4 hours
Do BAC threshold changes work? Journal of Policy Analysis and Management (2001) study by Thomas Dee 5% reduction in fatal accidents for states that moved to 0.10 7% reduction in fatal accidents for states that initially enacted a 0.08 threshold Journal of Policy Analysis and Management (2003) study by Eisenberg Observes that the differential between these two estimates is most relevant since it represents the marginal change from 0.10 to 0.08 Indicates the Dee estimates imply a 2% reduction in accidents stemming from a reduced BAC threshold from 0.10 to 0.08 In his own analysis the reduction in accidents is about 3% Somewhat puzzling According to NHTSA (2000): An adult driver with a BAC level between.08 and.10 BAC is 8.5 times more likely to cause a fatal accident than a driver with a 0 BAC An adult driver with a BAC level between.05 and.08 BAC is 4.7 times more likely to cause a fatal accident than a driver with a 0 BAC Wouldn'twe expect a greater reduction in fatal accidents than 2-3%? Question: Is there any evidence that drivers even react to lower BAC levels by changing drinking or driving behavior? 10 Potential insight to this question BE Press Economic Analysis and Policy (Carpenter and Harris 2005) Examine drinking behaviors following the move from 0.10 BAC thresholds to 0.08 thresholds. They observe a reduction in consumption among moderate drinkers They see no change in the likelihood of binge-drinking or alcoholinvolved driving. The latter outcome presents some difficulties in reconciling these behavioral responses with lower fatality rates found by Dee and Eisenberg. Question of Interest Do we observe important behavioral changes in seatbelt usage among intoxicated drivers following the concurrent enforcement of stricter BAC thresholds and primarily enforced seatbelt laws? However, if alcohol-impaired drivers increase seatbelt usage, it would reduce fatalities without necessarily reducing drunk driving.
Data: Fatality Analysis Reporting System (FARS) FARS is maintained by NHTSA to monitor automobile accident trends in the U.S. Provides near census of all fatal accidents in the U.S. Accident, Vehicle, and Person-level data Includes non-self-reported information on the blood alcohol content (BAC) and seatbelt usage of all drivers Given our focus on seatbelt laws, we only use FARS accident data that involve passenger vehicles (as defined by the NHTSA), which include cars, light trucks, and vans Time Period: 1991 2010 Indexed change in the seatbelt usage rate 0.02.04.06.08 Figure 2: Event Study -10-5 0 5 10 Quarters pre- or post-treatment Treatment States Control States 13 14 Driver-level analysis with FARS SBU ist = α s + τ t + X ist β + δpbl st + γba08 st + ΨBAC08 st *PBL ist + ε ist SBU is a dichotomous variable indicating that a driver in a fatal accident uses a seatbelt (Probit) PBL is a dummy variable indicating a state has a primarily enforced seatbelt law in effect at the time of the accident BA08 is a dummy indicating a BAC laws of 0.08 is in effect in the state (as opposed to a 0.10 law) Ψ measures the interaction between PBL and BA08 X ist individual or accident level characteristics (age, gender, weather, daytime, vehicle type, speed limit) α s state fixed effects τ t year-month fixed effects Standard errors are clusters at the state level BAC 0.08 and Primary Enforcement Law Effects on BA08 PBL BA08 and PBL 15 16
BAC 0.08 and Primary Enforcement Law Effects on BA08-0.0320 (0.0315) PBL 0.118*** (0.0352) BA08 and PBL 0.0805** (0.0329) Observations 125,983 BAC 0.08 and Primary Enforcement Law Effects on Marginal Effects BA08-0.0320 0.0013 (0.0315) PBL 0.118*** 0.0507 (0.0352) BA08 and PBL 0.0805** 0.0259 (0.0329) Observations 125,983 17 18 BAC 0.08 and Primary Enforcement Law Effects on BA08 PBL BA08 and PBL Sober Drivers BAC 0.08 and Primary Enforcement Law Effects on BA08-0.0320 (0.0315) PBL 0.118*** (0.0352) BA08 and PBL 0.0805** (0.0329) Sober Drivers 19 Observations 20 Observations 125,983
BAC 0.08 and Primary Enforcement Law Effects on Sober Drivers BA08-0.0320-0.0004 (0.0315) (0.0323) PBL 0.118*** 0.173*** (0.0352) (0.0437) BA08 and PBL 0.0805** -0.0135 (0.0329) (0.0432) BAC 0.08 and Primary Enforcement Law Effects on Sober Drivers Drunk vs. Sober BA08-0.0320-0.0004 (0.0315) (0.0323) PBL 0.118*** 0.173*** (0.0352) (0.0437) BA08 and PBL 0.0805** -0.0135 (0.0329) (0.0432) Drunk Driver BA08 and Drunk Driver PBL and Drunk Driver BA08 and PBL and Drunk Driver 21 Observations 125,983 211,571 22 Observations 125,983 211,571 BAC 0.08 and Primary Enforcement Law Effects on Sober Drivers Drunk vs. Sober BA08-0.0320-0.0004-0.0007 (0.0315) (0.0323) (0.0321) PBL 0.118*** 0.173*** 0.173*** (0.0352) (0.0437) (0.0436) BA08 and PBL 0.0805** -0.0135-0.0133 (0.0329) (0.0432) (0.0432) Drunk Driver -0.595*** (0.119) BA08 and Drunk Driver -0.0313 (0.0355) PBL and Drunk Driver -0.0550 (0.0402) BA08 and PBL and Drunk Driver 0.0933** 23 (0.0457) Observations 125,983 211,571 337,552 Issue with using the FARS Someone has to die in accident for us to observe the driver. Hence, this is a selected sample of particularly dangerous drivers and situations. Bias likely works against finding an increase in seatbelt use if seatbelts are saving lives; that is, we should find a lower proportion of belted drivers. Can t confirm this so turn to BRFSS for robustness. 24
Behavioral Risk Factor Surveillance System BRFSS is maintained by the CDC to monitor health and behavioral risk in the U.S. Population BRFSS positives It draws a random sample of the population, rather than just people who were in fatal automobile accidents. Contains detailed information on seatbelt use and drinking behavior than just the one-time read one gets from the FARS. BRFSS negatives It does not measure whether the affected seatbelt users were actually making simultaneous drinking, driving, and seatbelt decisions. Self-reported retrospective information 25 Behavioral Risk Factor Surveillance System Variable of interest is seatbelt usage 26 How often do you use seatbelts when you drive or ride in a car? Would you say... as one of the following frequencies: Always, Nearly always, Sometimes, Seldom, and Never Demographic variables on: age, gender, race, education, income, employment status, etc. BRFSS waves: 1990-1998, 2002, 2006, 2008, 2010 Individual-level analysis with BRFSS SBU ist = α s + τ t + X ist β + δpbl st + γba08 st + ΨBAC08 st *PBL ist + ε ist SBU is ordered measure of seat belt use frequency (Ordered Probit) PBL is a dummy variable indicating a state has a primarily enforced seatbelt law in effect at the time of the accident BA08 is a dummy indicating a BAC laws of 0.08 is in effect in the state (as opposed to a 0.10 law) Ψ measures the interaction between PBL and BA08 X ist individual characteristics (age, gender, employment status, income, race, marital status, smoker) α s state fixed effects τ t year-month fixed effects Standard errors are clusters at the state level BAC 0.08 and Primary Enforcement Law Effects on, BRFSS: Ordered Probits BA08 PBL BA08 and PBL Any binge drinking No drinking 27 28 Observations
BAC 0.08 and Primary Enforcement Law Effects on, BRFSS: Ordered Probits Any binge drinking No drinking BA08-0.0264-0.0115 (0.0311) (0.0365) PBL 0.1213** 0.1162** (0.0565) (0.0454) BA08 and PBL 0.0713 0.0177 29 (0.0560) (0.0503) Observations 845,860 215,364 BAC 0.08 and Primary Enforcement Law Effects on, BRFSS: Ordered Probits Any binge drinking No drinking Combined BA08-0.0264-0.0115-0.0114 (0.0311) (0.0365) (0.0368) PBL 0.1213** 0.1162** 0.1173** (0.0565) (0.0454) (0.0456) BA08 and PBL 0.0713 0.0177 0.0166 30 (0.0560) (0.0503) (0.0506) BINGE30-0.5055*** (0.0626) BA08 and BINGE30-0.0154 (0.0228) PBL and BINGE30 0.0003 (0.0299) BA08 and PBL and BINGE30 0.0569** (0.0280) Observations 845,860 215,364 1,061,224 Any evidence of policies saving lives? We move back to the FARS data to compile accident counts by state-month cell Hypothesis: There will be fewer alcohol-related accidents resulting in fatalities. Problem with calculating alcohol-related accidents: BAC content is not measured for all accidents The highly reliable imputation procedure uses seatbelt use as a primary predictive variable We therefore identify accidents most likely affected by the interaction of seatbelt laws namely accidents between 6PM and 6AM. These are most patrolled times and most likely to see drunk driving Falsification exercise: daytime accidents during the week as an alternative. 31 State-level analysis of Accidents with FARS Ln(Acc) st = α s + τ t + X st β + δpbl st + γba08 st + ΨBAC08 st *PBL st + ε st Acc is the total of passenger-vehicle accidents in each state-month PBL is a dummy variable indicating a state has a primarily enforced seatbelt law in effect at the time of the accident BA08 is a dummy indicating a BAC laws of 0.08 is in effect in the state (as opposed to a 0.10 law) Ψ measures the interaction between PBL and BA08 X st area controls (state population, beer tax rates, unemployment rates) α s state fixed effects τ t year-month fixed effects Standard errors are clusters at the state level Estimations are weighted by the number of accidents to limit the undue influence of low-frequency, high variance states. 32
Impact on State-Level Fatal Accidents Nighttime (6PM 6AM) BA08 PBL BA08 and PBL State Population in (100,000) State Beer Tax State Unemployment Rate Observations 33 Ln Accidents Impact on State-Level Fatal Accidents Nighttime (6PM 6AM) Ln Accidents BA08 0.0417* (0.0242) PBL 0.0229 (0.0374) BA08 and PBL -0.0740** 34 (0.0342) State Population in (100,000) 0.0025* (0.0013) State Beer Tax -0.530** (0.210) State Unemployment Rate -0.0008 (0.0082) Observations 12,101 Impact on State-Level Fatal Accidents Nighttime (6PM 6AM) Daytime/Weekdays (6AM 6PM) Ln Accidents Ln Accidents BA08 0.0417* 0.0679*** (0.0242) (0.0245) PBL 0.0229-0.00394 (0.0374) (0.0440) BA08 and PBL -0.0740** -0.0362 35 (0.0342) (0.0416) State Population in (100,000) 0.0025* 0.0020 (0.0013) (0.0017) State Beer Tax -0.530** -0.241 (0.210) (0.148) State Unemployment Rate -0.0008-0.0102 (0.0082) (0.0071) Observations 12,101 11,912 Conclusions so far Consistent with previous studies on traffic safety: 1. We find that seatbelt laws are much more effective in terms of reducing fatalities if they are primarily enforced. 2. Implementation of lower blood alcohol content (BAC) thresholds are less effective than advocates hope. New findings: 1. Inebriated drivers are much more likely to increase their seatbelt use once BAC thresholds are enacted if there are primarily enforced laws in place 2. There are fewer fatal drunk driving accidents following lower BAC thresholds laws when primarily enforced seatbelt laws exist. 3. Suggests that many lives are of drunk drivers or passengers of drunk drivers (externality still persists) 36
Questions? Thank You 37 38 Effects of other variables on seat belt use Age 0.00170* (0.000927) Male -0.202*** (0.0133) Good Weather -0.0811*** (0.0109) Daytime 0.0528*** (0.0148) Vehicle Type: Car 0.229*** (0.0124) Speed Limit <30-0.259*** (0.0342) Speed Limit 30-39 -0.142*** (0.0347) Speed Limit 40-49 -0.0788* (0.0408) Speed Limit 50-59 -0.185*** 39 Speed Limit 60+ (0.0294) @ BAC 0.08 and Primary Enforcement Law Effects on Estimates, FARS Partial Effects Drinkers Non-Drinkers Drinkers vs. Non- Drinkers Interaction BA08 0.0013-0.0020-0.0008 PBL 0.0507 0.0611 0.0571 BA08 and PBL (cross-partial) 0.0259-0.0046 n/a BA08 and PBL and Drunk Driver n/a n/a 0.0302 40
Ordered Probit Partial Effects, BRFSS Ordered (Ordered Probit) Predicted Outcome: Never Seldom Sometimes Nearly Always Always BA08 and PBL cross-partial, binge drinkers -0.0053-0.0039-0.0054-0.0065 0.0211 BA08 and PBL cross-partial, non-drinkers -0.0012-0.0007-0.0012-0.0018 0.0049 BA08 and PBL and Binge drinker cross-partial -0.0052-0.0027-0.0041-0.0050 0.0170 seatbelt usage rate; drunk drivers.05.1.15.2.25 Figure 1: Trend Comparison 1991.1 2000.4 Period Treatment States Control States 41 42