Interstate 40 is one of the nation's great east-west highways. If a traveler has the time and inclination, he or she could drive on it from Wilmington, N.C. on the Atlantic coast to Bartow, Calif., almost to the Pacific Ocean. Or could have. Such a trip is impossible at the moment.

A major rock slide near the Tennessee-North Carolina border has blocked the road in both directions. The highway, officials report, could be shut down for up to four months as crews work to clean up and then repair the roadway. The cost of that work will be significant, as will the financial losses to those whose livelihood depends in whole or part on business from I-40 travelers. The inconvenience to those accustomed to using the route for either short or long jaunts will be considerable, as well.

There's already considerable evidence extant showing how costly and inconvenient the 500,000-ton rock slide just a couple of miles from the states' border will be. A spokesman for the North Carolina Transportation Department says the cleanup and repair ultimately could cost $10 million, if not more. The financial toll does not end there.

The slide, which miraculously did not cause either serious injuries or deaths to passing motorists, occurred at the height of tourist season. Businesses dependent on fall travelers for a major part of yearly revenue are reporting steep declines in customers. The longer the road remains closed, the more painful the reductions in revenue at businesses along or near the roadway are likely to be. Some operators already worry about being unable to survive the slide-induced slowdown.

I-40 usually carries about 20,000 vehicles a day. Many are trucks that transport goods from the Carolinas into Tennessee or to points farther west. That interstate commerce will still take place, but it will be more time consuming and thus costly. The posted detour around the slide is longer by more than 50 miles than the more direct I-40 route. On days when traffic is heavy or the weather inclement -- dense fogs and, as winter nears, snow are not uncommon -- delays along the detour are likely.

Detours and delays, of course, are the legacy of the slide as far as motorists are concerned. Those who hoped to make a quick trip along I-40 to Knoxville for the recent UT-South Carolina football game, for example, were unable to do so. The detour added well over an hour to the journey in many instances. Until the road is cleared and the mountainsides above it stabilized, I-40 travelers can expect comparable constraints.

Considerable work will be necessary before I-40 can be reopened. Slides in the past have taken up to several weeks to repair, but this one appears far more extensive. Officials say the current closure could be the longest in the mountain highway's 40-year history. There's no way to rush the clean-up and repair..

The slide took place in an area where the roadway follows a course through steep walls. Removing the debris in a manner that protects workers and the roadbed is difficult. Once that's done, stabilizing the slopes to reduce the risk of a similar calamity in the future will be the next step. How long that will take, how much it will cost and when I-40 will reopen remain open questions.