Why Are Traffic Deaths On The Rise?

After decades of a massive secular decline in traffic deaths, reaching an all-time record low in 2014 per VMT as well as per capita, such deaths have been creeping up again since then.  2015 and 2016 both saw national increases in fatalities, and 2017 looks likely to continue that grim trend (and indeed has in several states).  In fact, it is the largest two-year jump in deaths in half a century.  So why has progress stalled and begun to reverse in recent years?

The list of most likely factors includes the following:

• Lower gas prices
• An improving economy since the Great Recession
• An increase in distracted driving (and walking), primarly from smartphones
• Higher speed limits than in the past 
• Infrastructure in disrepair from neglect
• Slacking on traffic safety improvements in general since the early 1990s

All of these things are true, and all of them are known to be correlated with traffic casualties.  Other factors are involved as well, to be sure, but these are the big ones.  The first three are the proximal causes, while the last three are the more distal ones.

Of course, drunk driving and not wearing seatbelts remain rather persistent contributors to the number of these deaths, but such behaviors remain far lower than they were decades ago.  Nevertheless, they remain at dangerous levels, and it is apparently a bit too early to feel safe in that regard.  And with real alcohol prices at record lows today and alcohol consumption on the rise for the past two decades, there is definitely a cause for concern in that regard.

What about drugged driving, then?  Is it really on the rise, like some have claimed?  Perhaps, but it may simply be that we are getting better at detecting it rather than an actual increase.  Or perhaps it is a bit of both.  The opioid epidemic certainly doesn't make the roads any safer.  And contrary to the anti-legalization folks, there does not seem to be any firm link between cannabis legalization and traffic fatalities.  In fact, some studies have found decreases in highway deaths following cannabis liberalization, due to an apparent substitution with alcohol.

One thing is for sure.  Whether this spike in traffic casualties is a short-term blip or the start of a longer-term trend (which will only be known in hindsight), it should be a major wake-up call that we clearly cannot afford to be complacent about it any longer.

In Other News, New Study Finds That The Sun Rises In The East

Captain Obvious called, and they want their study back.  Namely, the one that found that more frequent police traffic stops in general leads to less drunk driving.  In fact, communities with very few traffic stops had a rate of impaired driving that was as much as two to three times higher than in communities with more frequent traffic stops.  The same was true for the intensity of DUI saturation patrols, which, interestingly enough, were found to be quite superior to roadblock-style sobriety checkpoints in this study.

Additionally, they also found that the number of DUI arrests, after other variables controlled for, was also inversely correlated with drunk driving despite the chicken-or-egg problem inherent in this measure.  Thus, on balance, the greater the probability of arrest if one does drive drunk in a given community, the less people are willing to drive drunk in that community.

Again, we see that the perception of swift and certain punishment--that is, greater odds of getting caught--does indeed act as a robust deterrent for drunk driving.  Gee, who woulda thunk it?

So how about the following thought experiment:  if the drinking age was suddenly lowered to 18 overnight, how would police respond now in 2018?  Most likely, they would become more active in cracking down on DUI, fearing an increase in such among young people.  And that crackdown would not only prevent the feared short-term increase in traffic casualties, but also have a spillover that would reduce traffic casualties among all ages.  That is the most logical prediction of the net effect of doing so nowadays, as it's clearly not the 1970s anymore.

It's time to finish the job.   So what are we waiting for?

A Critique of Barnum et al. (2012)

A new study by Barnum et al. (2012) on drinking age law enforcement was recently published online this month.  In this first-of-its-kind study, using data from 1975-2006 they find that birth cohorts exposed to tougher enforcement of PAULA (possession of alcohol under the legal age) laws (as measured by underage drinking arrest rates) from ages 15-20 had modestly lower arrest rates for assault and vandalism between the ages of 15-24.  This remained true even when age effects, period effects, relative cohort size, and percentage of nonmarital births were controlled for.   But was it really a causal relationship?

While the authors appear to be convinced that this relationship is causal, we at Twenty-One Debunked note that there are plenty of reasons that this relationship could easily be spurious.  For example:

• Several other potentially important variables were not controlled for, including ones that may not have been captured by age and period effects.
• State-to-state variation was not explored at all.
• Arrest rates may have given biased estimates due to underreporting and changes in reporting rates and police practices over time, which can yield specious inferences.
• The strengths of the underage drinking laws themselves were not explored, only the enforcement of such laws as measured by arrest rates.
• Cohorts exposed to drinking ages of 18, 19, 20, and 21 were all lumped together, with no attempt to distinguish between them.
• No other crimes were explored besides assault and vandalism, and no distinction was made between types of assault (i.e. simple vs. aggravated).
• Allocating more resources towards arresting underage drinkers (and those who commit other victimless crimes) takes away from resources used to fight real crime, including assault and vandalism.  So, an increase in the former could lead to a spurious decrease in arrests for the latter in the absence of any real change in the latter.

Even if we accept the authors' conlcusions at face value, arresting underage drinkers does not appear to be a particularly cost-effective crime reduction strategy from a public safety standpoint.  The study reported that for every full unit increase in underage drinking arrests, there was only a 0.125 unit decrease in assault arrests and a 0.134 unit decrease in vandalism arrests.  Other sources note that on average, for every 1000 or so incidents of underage drinking, only one PAULA arrest occurs, making it a highly inefficent use of resources.  Law enforcement resources would thus be better spent actually targeting real crimes rather than victimless ones like underage drinking.

The example of San Francisco is highly instructive in this regard.  In 1990-1992, they were a crack-infested, gang-ridden hellhole.  By 2000, violent crime had plummeted by half (and even more so for juveniles), and by 2009 they became one of the safest big cities in America.  And how did they manage to do this?  Did they employ a "broken-windows," zero-tolerance approach to the most minor offenses, especially by young people?  Hardly!  In fact, beginning in 1992 (the city's peak year for violent crime), they stopped enforcing their youth curfew law (which was completely abolished in 1995), and since then they have actually cut back on arresting young people for "status" offenses (such as underage drinking) and cannabis possession, making such offenses the lowest priorities.  In other words, "don't sweat the small stuff."   Meanwhile, the police freed up more resources to tackle serious crime, and managed to build better relations with the community.  While the exact reasons for the drop in crime are not entirely clear, and several other cities nationwide saw similar improvements, it certainly casts doubt on the authors' thesis that cracking down on underage drinking reduces crime.

Interestingly, 'Frisco teens also show significantly lower rates of violence, "binge" drinking, driving after drinking, drinking in general, cannabis use, huffing, and crack/cocaine use compared with the national average according to the Youth Risk Behavior Survey.   Furthermore, the rates in San Francisco are comparable to or lower than those in NYC (and dropped at a similar or faster rate) despite the latter city's notoriously heavy-handed police tactics under Mayors Giuliani and Bloomberg.