Do you know the way to Tennessee? Don't ask Bing.

It's coming on Christmas. They're cutting down trees. And Interstate 40 is still closed at the Tennessee border, because of an Oct. 25 rock slide.

NCDOT is using dynamite and dump trucks to remove tens of thousands of tons of boulders, to repair the roadway - and (hopefully) to stabilize the hillside so this won't happen again. I-40 won't reopen until spring.

If your holiday plans include a drive through the Smokies, you'll want to take care in choosing your route. (And if you've found a good one, please let me know by e-mail or in a blog comment below.)

NCDOT is sticking with its suggestion that drivers stick with interstate highways: I-26 west (north) from Asheville to Johnson City, Tenn., and I-81 south to rejoin I-40 east of Knoxville. It adds 53 miles to the trip. (Here's an NCDOT page with rockslide updates, Twitter links and detour details.)

U.S. 441 and U.S. 25/70 may look like more direct drives on the map -- but both routes are twisty, narrow mountain roads frequently blocked with snow and ice. Definitely if you're driving 18 wheels, you don't belong on either of these routes.

What do the online mapping services say? A few weeks ago, some of them were still blind to the I-40 blockage. Now they mostly agree that the best route between Raleigh and Knoxville runs through southern Virginia.

Here are links to Raleigh-Knoxville directions, courtesy of ...

Google: Take I-40 to Winston-Salem, then US 52, I-74 and I-77 to I-81.

Yahoo: Ditto.

Mapquest: Ditto.

Traffic.com: Ditto.

Bing: What's this? Contradictory directions with a map routing you on I-40 all the way -- negated with pop-up boxes warning that I-40 is closed.

This "you can't get there from here" advice comes from the website touted by Microsoft as "your decision engine."