That didn’t turn out as planned…

You probably have seen those public service announcements on many motorways and highways around the world about the number of traffic deaths on that particular stretch of road. They have become commonplace in many countries as a way to alert drivers. 

The problem just is that often, the most dangerous stretches of road are the ones that tend to be very busy. And you don’t want to distract drivers with public service announcements when they should focus. Jonathan Hall and Joshua Madsen looked at electronic road signs in Texas that announced to drivers how many people died on the road this year.

Electronic road signs in Texas

Source: Hall and Madsen (2021).

Apparently, these signs are in some sense too effective, because the researchers found that the information they display is so salient that it distracts drivers and lowers their attention given to the ongoing traffic ahead of them. Whenever these messages were displayed, traffic accidents increased within 5 miles of the signs and then dissipated. If the traffic was heavier when the signs were displayed, accidents increased more. And once the signs were turned off again, the number of accidents declined as well.

And the scariest thing: The higher the fatalities announced on the electronic signs the more accidents increased. In January, the signs show the total for the previous year, while from February to December the signs show the cumulative total for the current year and thus show an increasing number every month. The chart below shows that on average the number of accidents increases every month, peaking in January when the highest numbers are shown. There is a strange summer effect that probably is due to drivers going on vacation but overall, the trend holds. 

Change in traffic accidents near signs by month

Source: Hall and Madsen (2021)

The overall cost for the Texas economy is not small. The authors estimate that the overall annual cost of these extra accidents is $380m. For the US overall, that would extrapolate to $2.3bn per year.

I don’t know about you, but I think these public service announcements and health and safety warnings have generally become a nuisance. There are way too many of them. If you want to drink bleach, be my guest. We don’t have to protect stupid people from themselves. Better to reduce the number of public service announcements and make sure they really work and don’t end up causing more problems like the Texas road signs. Sometimes, good intentions can be the opposite of good.