Across study after study, one factor appears in fatal wrong-way crashes more than any other: alcohol impairment.
The AAA Foundation's analysis of fatal wrong-way crashes on divided highways from 2014 through 2023 identified alcohol-impaired drivers as one of the clearly elevated-risk groups, alongside older drivers, drivers without valid licenses, and drivers of older vehicles.
Understanding why impairment produces this specific error explains a lot about what prevention has to do.
Why impairment produces this particular mistake
Entering a highway in the wrong direction is not a typical impaired-driving error. Impairment is usually associated with lane departure, delayed reaction, and misjudged speed. A wrong-way entry is a navigational failure — a decision, made at a specific point, that was wrong from the start.
Several effects of alcohol converge to make it likelier:
Degraded visual processing at night. Alcohol reduces the ability to interpret complex visual scenes, particularly in low light. An interchange at night is a complex visual scene: multiple ramps, signs at varying angles, headlights from several directions.
Narrowed attention. Impairment tends to focus attention on what is directly ahead at the expense of peripheral information. Wrong-way signage and ramp markings often sit exactly in that peripheral field.
Reduced error detection. Perhaps most importantly, impairment reduces the ability to notice that something has gone wrong. An unimpaired driver who enters a ramp incorrectly typically registers within seconds that the signs are facing the wrong way and the geometry is off. That self-correction is precisely the function alcohol degrades.
That last point explains why detection systems matter so much. The population most likely to make this error is also the population least likely to catch it themselves.
The compounding conditions
Impairment rarely appears alone in these crashes. The research points to a cluster of conditions that overlap heavily: nighttime and dawn/dusk hours, drivers unfamiliar with the area, and rural roads.
These are not independent factors — they co-occur. Late at night, on an unfamiliar road, in poor light, with impaired judgment, at an interchange designed to be read quickly. Each condition on its own is manageable. Together they produce the crash type.
What this means for intervention
Signage has to work for degraded processing. Standard signs are designed for an alert driver scanning normally. Interventions aimed at this problem — large illuminated wrong-way signs, flashing LEDs, red retroreflective markers low in the field of view — are designed to be noticed by someone who is not scanning normally. This is why the illuminated signs in Arizona's detection system trigger automatically rather than relying on standard static signage alone.
Automatic detection matters more than driver self-correction. If the driver cannot be relied on to notice the error, something else has to notice it. That is the core argument for camera-based detection.
Warning other drivers is essential. Since the wrong-way driver may not correct, the people at risk need to know. Getting that warning out quickly is often the intervention that actually prevents the collision.
The prevention that happens earlier
None of the above addresses the actual root cause, which is someone impaired getting behind a wheel.
Everything discussed here is downstream mitigation of a decision made earlier in the evening. The ride-share that gets taken, the keys handed over, the friend who says something — those prevent the entire chain, and they are more effective than any technology deployed afterward.
We work on the technology side because the earlier interventions do not catch everyone and never will. But it is worth being clear about the order of effectiveness. The most reliable way to prevent a wrong-way crash is for an impaired person not to drive at all.