It’s easy to believe that when it comes to safety, the more messaging you do, the more safe people will be.
Whether it’s in the workplace, working outdoors, playing sports, or driving your car, the conventional wisdom is that safety messaging always works and is effective. Letting people know about how safe or dangerous an activity is can only be helpful.
Right?
Time to turn that conventional wisdom on its head…
Jonathan Hall and Joshua Madsen from the University of Toronto and the University of Minnesota, respectively, examined the effectiveness of the safety messaging flashed to drivers on highway signs. The conventional wisdom is that safety messaging on these highway signs helps to keep drivers vigilant and more safe while driving.
“Stay alert, arrive unhurt.”
“Seatbelts save lives. Buckle up.”
“7 people died on Texas highways last month. Stay alert.”
Most drivers have seen these kinds of messages on electronic highway signs where they live. These kinds of messages seem innocuous. They’re just educational or simple reminders about driver safety.
But what if such highway safety messaging has unintended consequences?
The Unintended Consequences of Highway Safety Messaging
Electronic highway signs are called “dynamic message signs” (DMSs) by the researchers. These researchers describe the experiment they designed to determine how traffic accidents might be related to the messages displayed on these kinds of signs.
Specifically, they wanted to understand how messages that were general safety messages (such as “Buckle up!”) differ from messages that display the year-to-date number of statewide highway fatalities. They conducted their analysis in Texas.
Texas provides an ideal setting because the Texas Department of Transportation (TxDOT) decided to show fatality messages starting in August 2012 for 1 week each month: the week before TxDOT’s monthly board meeting (campaign weeks).
This allows us to measure the impact of the intervention, holding fixed the road segment, year, month, day of week, and time of day. We used data on 880 DMSs and all crashes occurring in Texas between 1 January 2010 and 31 December 2017 to investigate the effects of this safety campaign.
We estimated how the intervention affects crashes near DMSs as well as statewide. As placebo tests, we estimated whether the chosen weeks inherently differ using data from before TxDOT started displaying fatality messages and data from upstream of DMSs.
The Findings: Messaging Increases Traffic Crashes
According to the researchers, “Contrary to policy-makers’ expectations, we found that displaying fatality messages increases the number of traffic crashes.”
Driving closer to the sign messaging made crashes more likely: “Campaign weeks realize a 1.52% increase in crashes within 5 km of DMSs, slightly diminishing to a 1.35% increase over the 10 km after DMSs.”
We used instrumental variables to recover the effect of displaying a fatality message and document a significant 4.5% increase in the number of crashes over 10 km.
The effect of displaying fatality messages is comparable to raising the speed limit by 3 to 5 miles per hour or reducing the number of highway troopers by 6 to 14%.
Why Does This Specific Kind of Messaging Increase Accidents?
The researchers offered at least one possible explanation: “…[T]hese “in-your-face,” “sobering,” negatively framed messages seize too much attention, interfering with drivers’ ability to respond to changes in traffic conditions.” In short, drivers get distracted by the signs and — more worryingly — their specific cognitive attention gets temporarily distracted.
This is the same cognitive focus that is needed to pay attention to roadway conditions and drive defensively on highways at high speed. In short, the sign offers too much emotionally-charged information that’s directly relevant to drivers. Reminding drivers that they could be just another fatality statistic isn’t scaring a driver “straight” — it’s causing them to worry, increasing their anxiety levels, and taking brain cycles away from paying attention to the driving conditions.
The researchers conclude:
Supporting this explanation, we found that displaying a higher fatality count (i.e., a plausibly more attention-grabbing statistic) causes more crashes than displaying a small one, that fatality messages are more harmful when displayed on more complex road segments, that fatality messages increase multi-vehicle crashes (but not single-vehicle crashes), and that the impact is largest close to DMSs and decreases over longer distances.
Sometimes you need a scientific study to demonstrate why maybe the seemingly good idea — alerting drivers to statewide driving fatalities — isn’t always so good.
Reference
Hall, JD & Madsen, JM. (2022). Can behavioral interventions be too salient? Evidence from traffic safety messages. Science, 376, 6591. DOI: 10.1126/science.abm3427
Image: JD Hall
