These are the average scores on a 20-question driver's test administered to more than 5,000 licensed drivers in a survey commissioned by the GMAC Insurance.

Ranking	States	Score
1	Oregon	89.4
2	Washington	88.4
3	Iowa	87.7
4	Idaho	87.5
5	Wyoming	87.4
6	Vermont	86.6
7	Nebraska	86.5
8	Wisconsin	86.3
9	Montana	86.2
10	West Virginia	86.2
11	Minnesota	86.1
12	North Dakota	85.6
13	North Carolina	85.2
14	Indiana	85.1
15-tie	Alabama	84.7
15-tie	Virginia	84.7
15-tie	Nevada	84.7
16	Missouri	84.7
19-tie	Ohio	84.3
19-tie	South Dakota	84.3
21	Colorado	84.2
22	Kansas	84.0
23	Michigan	83.8
24	New Hampshire	83.7
25	Tennessee	83.4
26	Maine	83.2
27-tie	Arkansas	83.1
27-tie	South Carolina	83.1
29-tie	Georgia	82.9
29-tie	New Mexico	82.9
31	Oklahoma	82.8
32	Texas	82.7
33-tie	Utah	82.6
33-tie	Arizona	82.6
35-tie	Mississippi	82.5
35-tie	Delaware	82.5
35-tie	Kentucky	82.5
38	Pennsylvania	82.1
39	Louisiana	81.7
40	Illinois	81.6
41	Florida	81.1
42	Connecticut	80.9
43	California	80.4
44-tie	Maryland	79.8
44-tie	Washington, DC	79.8
44-tie	New York	79.8
47	New Jersey	78.3
48	Massachusetts	77.2
49	Rhode Island	77.0
National Average		82.7

The GMAC Insurance National Driver's Test found that nearly 20 million Americans, or about 1 in 10 drivers, would fail a state driver's test if they had to take one today. GMAC Insurance is part of General Motors' finance subsidiary, GMAC.

More than 5,000 licensed drivers between the ages of 16 and 65 were administered a 20-question written test designed to measure basic knowledge about traffic laws and safety. They were also surveyed about their general driving habits.

Drivers in the Northeast and mid-Atlantic states did worst. Twenty percent of test-takers failed there.

The state of Rhode Island leads the nation in driver cluelessness, according to the survey. The average test score there was 77, just eight points above a failing grade.

Those in neighboring Massachusetts were second worst and New Jersey, third worst.

Northwestern states had the most knowledgeable drivers. In those states, just one to three percent failed the test. Oregon and Washington drivers knew the rules of the road best. In Oregon, the average test score was 89.

According to the study, many drivers find basic practices, such as merging and interpreting road signs, difficult.

For instance, one out of five drivers doesn't know that a pedestrian in a crosswalk has the right of way, and one out of three drivers speeds up to make a yellow light, even when pedestrians are present, the study said.

Drivers not only lack basic road knowledge, but exhibit dangerous driving behavior as well.

"As a nation of drivers, we've made little progress in the past 10 years to curb some of the most dangerous driving behaviors, including drinking and driving and speeding," said Susan Ferguson, senior vice president of research at the Insurance Institute for Highway Safety.

One out of 10 drivers regularly exceeds the speed limit by 11 or more miles per hour, with drivers aged between 18 and 24 years showing the greatest propensity for speeding, the study said.

Speeding increases both the likelihood of an accident and the severity of the crash, the company added, citing research from IIHS.

Younger drivers are the most likely to fail a written driving test while those between the ages of 50 and 64 are the most likely to pass.