Yes, bicyclists are permitted to ride 'two abreast' in Seattle, meaning that two bicyclists may ride side-by-side in the same lane on a given roadway or sidewalk in the city. Motorists are often surprised to see bicyclists riding this way, especially in busy metropolitan areas like downtown Seattle, but it is completely legal in our city.
However, the City of Seattle's bicycle code prohibits bicyclists from riding more than two abreast on roadways or sidewalks. So the maximum number of side-by-side bicyclists legally permitted to ride in the same lane would be two, and any more than that could lead to a traffic infraction.
The exception to this rule is when bicyclists are riding on designated paths or roadways that are exclusively set aside for the use of bicycles.
More from the city's bike code:
"Riding more than two abreast is prohibited. Persons operating bicycles upon a roadway or sidewalk shall NOT ride more than two abreast except on paths or parts of roadways set aside for the exclusive use of bicycles."
Furthermore, city code dictates that bicyclists do not have the right of way at 4-way stops. If traffic control signals or signs exist, they must be adhered to. The first vehicle to arrive at an intersection or that is already in the intersection, has the right of way.
When two vehicles (either motor vehicles or bicycles) approach or enter an uncontrolled intersection that has no traffic signals or signs present from different directions at approximately the same time, the operator of the vehicle on the right has the right of way.
Washington state law also dictates that bicyclists may ride 'two abreast' on sidewalks and roadways, but no more than two riders may ride abreast. Again, state law also says the exception to this rule is in areas exclusively designed to be used by bicyclists.