With the summer "driving season" almost upon us, a startling new survey finds that about 20 percent of American motorists — close to 38 million people — don’t know enough to pass a written driving test.

GMAC Insurance put 20 questions before some 5,000 licensed drivers from all 50 states and the District of Columbia. CNN/Money reports that the average score was 76.2 percent, reflecting a slight dip from 2009. That’s apparently the good news. Meanwhile:

Nearly three out of four couldn’t identify safe following distances and some 85% incorrectly responded to questions about what to do when approaching a steady yellow light. This signals that licensed drivers lack knowledge of fundamental road rules, GMAC Insurance said.

One in four drivers admitted to "talking on a cell phone, eating, or adjusting their radios or iPods" while driving, and five percent said they text from behind the wheel — a "surprisingly low" number that probably says more about successful social stigmatizing than actual habits. 

On average, Midwestern drivers scored highest on the test, with Northeasterners faring the worst. According to the survey, drivers in Kansas are the most informed, while the most ignorant are in New Jersey — ranking just two spots below New York license-holders.

As a licensed driver who hasn’t taken a written test since age 16, I can’t help wondering how well I would do. If you’re curious yourself, you can take the test here.