If you are a full-time worker who lives in Fairfax County, chances are you drive to work alone and it takes you just under half an hour to cover the 12 miles to your job.

That profile of a typical Fairfax commuter, offered in a new county transportation report, spells trouble for the new Fairfax County Board of Supervisors, many of whose members ran on platforms promising to improve the county's transportation woes.

The report, a survey of county commuting patterns, suggests that county residents are so wedded to their cars that the only way to improve traffic conditions significantly may be by building new roads. And although some officials say the county needs more public transportation and car pools, the survey results suggest that many people don't use alternative transportation even if it's available.

The county's commuting habits are part of an April transportation survey answered by 7,561 county residents that is scheduled to be presented to the Board of Supervisors Monday, at the first meeting of the new board under the chairmanship of Democrat Audrey Moore.

The survey, conducted by the county's Office of Research and Statistics and Office of Transportation, was designed to provide a more complete statistical foundation upon which the county can design and build a better transportation network, according to County Executive J. Hamilton Lambert.

"I think what the survey shows is that there is still a great deal of resistance on the part of people to leave the freedom of their individual vehicles," Lambert said, noting that over 70 percent of the county's estimated 337,351 full-time workers drive to work alone.

The survey also shows that, in some areas of the county, mass transit is not available or underused and that "car pooling is still not anywhere near as effective as it could be or should be," Lambert said. Car or van pools are used by 14.2 percent of the county work force, while 9.9 percent use some form of mass transit.

The survey also sheds light on why the county's roads are so clogged. Of the estimated 148,624 residents who travel to a job in the county, 90 percent drive to work alone, 1.7 percent use public transportation and 6.3 percent use car or van pools. About 92 percent of the estimated 21,758 county residents who work in Tysons Corner drive to work alone, while only 1.5 percent use public transportation, according to the survey.

Similarly, more than 50 percent of full-time students over the age of 16 drive to school alone while only 15 percent take a school bus.

Car and van pooling and mass transit are most often used by people headed to jobs in the regional core, defined as the District, Rosslyn, Pentagon-Crystal City and downtown Alexandria. About 26 percent use car or van pools -- mostly in the I-66 and I-95 corridors -- while 23 percent use public transportation and 49 percent drive alone.

The survey found that 44.2 percent of Fairfax residents work in the county, 22.9 percent travel to the District, 6.4 percent go to Maryland, and 23.9 percent work in Virginia but outside the county.

More people work in the District than any other place, followed by the Reston-Herndon-Sterling area of the county (with 7.1 percent of the total county work force) and Tysons Corner (with 6.5 percent of the county work force).

About half of the county work force spends at least 30 minutes commuting to work one-way; 15.6 percent spends between 45 and 59 minutes commuting and it takes more than an hour for 5.5 percent of the work force to get to work. About 10 percent get to work in less than 10 minutes.

The survey also found that, in general, about 60 percent of the people who live in the far western parts of the county also work in the county, compared to only 40 percent of the people who live inside the Beltway.

Workers in the western reaches also have the worst trips to work, averaging as long as 40 minutes and as far as 17 miles, while residents inside the Beltway have an average 9.7 mile trip and make it in 24 minutes.