The District signed an agreement yesterday under which a private company pledged to pay more than $150 million over 20 years for the right to erect hundreds of bus shelters that would be adorned with money-earning advertising posters.

Transportation Department officials said most of the income -- $100 million -- would help finance Mayor Anthony A. Williams's "Great Streets" program, which is intended to upgrade several of the city's principal transportation corridors.

The mayor, in a printed statement, called the new contract with ClearChannel Adshel, part of an international media giant, a "triple win for the District."

Williams (D) said the city's benefits would be cash; clean, new bus shelters; and money for Great Streets that would boost appearances and economic vitality.

Corridors to be improved with the shelter money include Pennsylvania Avenue SE, H Street and Benning Road NE, Nannie Helen Burroughs Avenue NE, Georgia Avenue and Seventh Street NW, Minnesota Avenue in Northeast and Southeast, Martin Luther King Jr. Avenue and South Capitol Street.

A Transportation Department spokesman said corridor upgrades would include new sidewalks, curbs and gutters, along with improvements to street lighting, trees and mass transit. Spokesman Bill Rice said the aim is to help attract stores, housing and jobs.

The city has two types of bus shelters: Metro's, which permit no advertising, and about 400 ClearChannel shelters, on which ads are sold. Those were built under an agreement that brought the city between $2 million and $3 million a year, Rice said.

The new contract provides for replacing the 400 ClearChannel shelters and adding 400 more within two years. The 800 shelters, to be built downtown and in city neighborhoods, are to be made of materials that resist graffiti and vandalism.

Neighborhood input will be sought on shelter construction. The structures will provide bus maps and electronic signs that will tell when buses will arrive.

Also proposed under the contract are automated facilities at which people could rent bicycles for short trips.

The arrangement requires final approval by the D.C. Council, Rice said.