SEATTLE — Downtown Seattle is facing another significant change to public transportation that will affect more than 30,000 daily bus commuters. 

The transit tunnel in downtown Seattle permanently closed to bus traffic on Saturday, and only light rail trains will travel underground. The move means more than 800 daily bus routes moved to downtown surface streets, potentially further clogging main city corridors.

The impacted routes are: 41, 74, 76, 77, 101, 102, 150, 252, 255, 257, 301, 308, 311, 316, and 550.

MAP: Bus stop changes on 2nd-6th Avenues

The long-planned change is the second phase of the “Seattle Squeeze,” which will allow for the construction of the new $1.7 million Washington State Convention Center expansion

Also see | Seattle breaks ground on new $1.7B Convention Center

The City of Seattle and King County have teamed up to try and find ways to help ease the pain. To help things move along, Metro will begin allowing all-door boarding along Third Avenue, which will feel part of the brunt of the switch. Riders who hold Orca cards will be able to board at any door.

“We’ve already installed fare readers on 21 of the corridors 31 bus stops along 3rd Avenue, and the final 10 will be in place by the end of this year,” said King County Executive Dow Constantine.

In the meantime, Constantine said boarding assistants would be at stops who can scan ORCA cards on the sidewalk during afternoon commutes so that you can board at any door.

WATCH: Seattle Mayor Jenny Durkan on bus changes

RELATED: Next chapter of 'Seattle Squeeze' pushing hundreds of buses onto downtown streets

While it doesn't sound like much, the idea is to streamline service along the transit-only corridor through the heart of downtown. During a demonstration on Thursday, Constantine showed how load time was cut in half when all bus doors were opened.

The changes also coincide with alterations made by the city of Seattle. The Seattle Department of Transportation has added a transit only, afternoon lane to several blocks of Fifth and Sixth avenues, which will also be seeing extra buses.

The bus changes are permanent but do not involve Sound Transit Link light rail, which will continue to use the downtown tunnel. However, Seattle Mayor Durkan said eventually traffic could improve after after additional light rail lines open and some bus lines can be eliminated. Light rail service is expected to extend to Northgate by 2021, to West Seattle by 2030, and to Ballard by 2035.

“We’re getting to a great place in Seattle, but it’s going to be tough getting there,” Durkan said.

The convention center isn’t expected to open until 2021.