cognitive bias

You are not as good a driver as you think.

Svenson (1981) found that 93% of the U.S. student sample believed they were in the top 50% of driving skill.

The study surveyed 161 university students, not 810 general drivers.

Your belief in your own superiority is a standard psychological blind spot.

Where this comes from

Study: Ola Svenson (1981)
What the check found: The 93% figure applies only to the U.S. student subset; the study involved 161 total participants, not 810, and students, not general drivers.
Confidence: Solid, with limits

One of these every day, and every one names the study it came from. When a finding is contested, it says so.