The car pool beat the solo commuter, the commuter beat the bus, and the bicyclist, who claimed the most fuel efficiency at 4.4 miles per whole wheat pancake, came in last.

It's official: Interstate 66 was the fastest, if not the most popular, commuting route for Northern Virginians on its first day of operation, according to an unscientific competition among Washington Post reporters.

The final 10-mile segment of I-66 opened yesterday after 26 years of planning and it appeared to be worth the wait, allowing Northern Virginians who could form the required four-person car pools to shave at least 10 minutes and a lot of aggravation off their daily commute to Washington.

A car pool of four left Fairfax City at 8:14 a.m. and reached downtown Washington well ahead of a Metro commuter, a bicyclist and a solo commuter car that left Fairfax City at the same time but traveled on Rte. 50, which was decorated like a Christmas tree with red and green traffic lights.

The car pool needed 31 minutes to travel from the Post News Bureau at 4103 Chain Bridge Rd. to the newspaper's main office at 1150 15th St. NW. The Rte. 50 travelers needed 40 minutes, the Metro traveler 49 minutes and the bicyclist (who actually began his trip at I-66 and the Capital Beltway), 51 minutes.

Race conditions were ideal for the I-66 travelers, since they had the curving, four-lane road virtually to themselves. The car pool passed six police cars, one highway maintenance truck, one television crew attempting a rolling interview, a boy on a bicycle watching the empty highway from an overpass, and just after the Leesburg Pike exit, one genuine commuter car pool group in a yellow station wagon.

On the $2.5 million I-66 bicycle trail, the Post bicyclist passed three joggers, two strollers and five Arlington residents walking a total of eight dogs, but no other bikers.

The car pool drove from the beltway to the Theodore Roosevelt Bridge in about 11 minutes. Even more impressive, the winning vehicle was not delayed at a stop light or stop sign until it reached 20th and E streets NW.

The Rte. 50 travelers, by contrast, needed 19 minutes to travel from beltway to bridge. They encountered traffic backups, although not serious ones, at usual bottlenecks such as Gallows Road, Annandale Road, and Seven Corners.

The Metro traveler reported a smooth journey that also took advantage of I-66. He caught the 1X bus, a rush-hour route, at the corner of University and Layton Hall drives, and rode it down Rte. 50, along the beltway to I-66, arriving at the Ballston Metrorail station at 8:42 a.m.. Buses have been using the new section of I-66 since June, shaving about 12 minutes off the 1X route time, Metro said. A Metro train pulled out of the Ballston station at 8:46, depositing the relaxed passenger at McPherson Square, six minutes from The Post, at 8:59.

None of the contestants accepted the race results with grace. The Rte. 50 travelers said the car pool's total time should include gathering all three passengers. The car poolers said the bus rider should include walking to the station in his total time. The bus rider said the Rte. 50 commuters encountered unusually sparse pre-Christmas traffic.

And the bicyclist, while making no excuses after his 13.2 mile trip, did point out that his breath in the 29-degree morning chill fogged his glasses and the rearview mirror on his helmet.