Can Behavioral Interventions Be Too Salient? Evidence From Traffic Safety Messages

Abstract

Behavioral interventions are an increasingly popular tool for encouraging socially desirable behavior. While they are expressly designed to seize people's attention, little consideration has been given to the costs of doing so. We estimate the consequences of seizing attention in the context of a widespread highway traffic safety campaign that displays roadside fatality counts on highway dynamic message signs (DMSs). We exploit detailed data on DMS and crash locations, DMS log files, and a unique setting in Texas where fatality messages are displayed only for one week each month. We find that this behavioral intervention significantly increases the number of traffic crashes. This increase is immediate, dissipates over 7 km, and increases with the displayed fatality count. Furthermore, drivers do not habituate to these messages, even after five years, and the effects do not persist beyond the treated weeks. Crashes increase statewide during treated weeks, inconsistent with any benefits. Our results show that behavioral interventions, designed to be salient, can crowd out more important considerations, causing interventions to backfire with costly consequences.

Keywords: behavioral intervention, nudges, salience, cognitive load, traffic safety, DMS

JEL Classification: D83, D91, H43, R41