RVs, commercial and agricultural vehicles were banned by the U.S. Capitol Police from roughly a 40-city-block area in the nation’s capital beginning Thursday (Oct. 11) — a move that’s expected to add to the current traffic delays caused by increased security measures after last month’s terrorist attacks.

Lt. Dan Nichols told CNN that RVs and the other types of vehicles were diverted beginning at 5 a.m. EDT Thursday from the following perimeter: 2nd Street on the east, 3rd Street on the west, Massachusetts Avenue on the north and D Street on the south.

Included in that area are the U.S. Capitol, all of the House and Senate office buildings, the U.S. Supreme Court, the Library of Congress and part of the National Mall. The White House is not inside the perimeter; the Department of Labor is just outside it.

Nichols said the ban was not prompted by any specific threat but was a preventative measure. He said the closures were indefinite and that authorities would re-evaluate the situation as needed.

Also inside the area are two major arteries that see heavy truck traffic daily: Independence Avenue and Constitution Avenue.

The ban includes any vehicle over one-and-a-quarter tons. Nichols said that would be equivalent to the size of a Fed-Ex delivery truck.

But, he said, it doesn’t affect Tour Mobiles, a train-like service that takes tourists around the capital. The city’s Metro Bus also is not affected by the ban, but officials have not yet decided if tour buses will come under the new restrictions.

“We feel that this is a balanced approach to meet our needs,” Nichols said.