The latest iteration of the One Center City plan considers 3rd Ave transit-only all day, a cycle track on 4th, and some 4th Avenue buses moved to 5th and 6th.

A delay in the convention center project gave bus riders a reprieve, as buses can use the Downtown Transit Tunnel until 2019. But as the “period of maximum constraint” rapidly approaches, the list of near-term projects to ease congestion is not yet final.

“We need to move on this fast,” said Tom Brennan, a consultant with Nelson Nygaard working with SDOT, King County Metro Transit, Sound Transit and the Downtown Seattle Association on the One Center City plan.

During the One Center City advisory group’s monthly meeting Thursday, Brennan presented the latest recommendations to ensure the city keeps moving when a handful of large construction projects begin.

To speed up bus travel times and improve reliability, Brennan said an all-day car ban was being considered for Third Avenue. Currently, during the week the street is reserved only for buses between 6 to 9 a.m. and 3 to 6:30 p.m. The proposed recommendations for Third Avenue would also extend the transit-only lanes north to Virginia Avenue and enable off-board fare payment at all stops between Jackson and Stewart Streets to allow for all-door boarding and lower dwell time.

After the group previously debating several options for a north/south bike lane, the latest recommendation places a protected two-way bike lane along the west side of Fourth Avenue between Main and Vine Street. SDOT anticipates the section between Seneca and Pine Street will be finished by the end of October. The segment from Pine to Vine Street would open in 2018, and the last portion between Main and Seneca Street by 2020.

To accommodate the future bike lane along Fourth Avenue, Metro buses (74, 76, 77, 301, 308, 311, 316) would be shifted to 5th and 6th Avenues. According to One Center City documents, shifting some buses off of Fourth Avenue will reduce northbound transit travel times for those buses by 15 to 20 percent.

Routes removed from Fourth Avenue would travel north in a contraflow lane along 5th until Marion Street, before turning east for one block and continuing on 6th. This change would eliminate three bus stops along Fourth Avenue, and add a new bus stop on Fifth Avenue at Columbia and two new stops on Sixth Avenue at Spring and Union.

According to One Center City documents, shifting buses off of Fourth Avenue reduces bus traffic by 30 percent along that street, eliminating the need for an extra bus lane to allow buses to pass each other.

These changes would reduce bus travel times along Fourth Avenue by about a minute, down from just over 10 minutes, according to One Center City documents. If the recommendations go through as presented Thursday night, the street would have two general purpose lanes, a parking and left turn lane and a two-way protected bike lane.

“The two-way protected bike lanes will be on the west side of Fourth Avenue,” spokesperson Mafara Hobson wrote in an email. “In general, parking or loading would be permitted on every other block (those for which a left-turn lane is not needed) during off-peak periods in the lane next to the protected bike lanes. Parking would be restricted during peak periods.”

Also under consideration by the agencies is extending the Fifth Avenue transit-only lane from Cherry to Marion and creating a transit-only lane along Sixth Avenue between Marion and Union Street.

A protected bike lane couplet is proposed for Pike and Pine between Second Avenue and Broadway. SDOT estimates the bike lane between Second and Eighth Avenue will be completed by October, and the last segment between Eighth Avenue and Broadway will be finished by 2020. Currently, the plan replaces the interim bike lane with a protected bike lane using planters rather than posts.

The One Center City group began meeting last September tasked with developing both a near-term and long-term comprehensive transit and traffic plan for downtown Seattle.