BOSTON -- A new study shows that one in six drivers on the road, roughly 36 million licensed Americans, would not pass their written DMV exam if taken today.

The third annual survey by GMAC Insurance gauges driver knowledge of the rules of the road by testing licensed Americans on actual questions from state DMV license exams.

According to this year's results, New York drivers ousted Rhode Island by ranking last in all 50 states and the District of Columbia on driver knowledge.

Idaho, on the other hand, topped the list and dethroned Oregon's tenure at first place as the most knowledgeable drivers in the United States.

While the national average score is 77.1 percent, New Yorkers had an average of 71 percent and the highest failure rates (36 percent); Idaho had an average score of 81.7 percent.

In general, geographical regions ranked similarly to previous years, with Alaska, Minnesota, Kansas and Wisconsin ranking in the top five and New Jersey, Washington, D.C., Massachusetts and Rhode Island in the bottom five among all states.

Other points of interest drawn from the study include:

With Age Comes Wisdom: The older the driver, the higher the test score. Drivers 35+ years old were most likely to pass.

More than half of respondents (55 percent) don't know how many feet to signal before making right or left turns.

More than 2 in 5 drivers (46 percent) are unaware of the meaning of a diamond-shaped sign (warning sign).

Fortunately, nearly all respondents (98 percent) know what to do when an emergency vehicle with flashing lights approaches, what to do when hydroplaning and the meaning of a solid yellow line.