The sharrows on Beach Drive in Seattle were painted northbound, as I discovered on my ride yesterday. I rode 2 abreast with another cyclist along the sharrows and got buzzed by one car, another zoomed past, and one waiting until it was clear in the other lane to pass. Sharrows are wide enough for 2 abreast, but I wouldn’t do that necessarily in heavy traffic.
Why not ride 2 abreast in heavy “traffic”? Bikes are traffic! People in cars can just be patient and pass when it is safe. Riding single file along beach drive and giving cars room to pass in the same lane puts the cyclist in the door zone. Beach Drive traffic is never heavy anyway. The only safe way to give cars and bikes room for total safety is to remove the private car storage along the side of the streets. Sometimes they call that parking, but it doesn’t look like a park to me!
I was referring specifically to not necessarily riding 2 abreast because there was a sharrow on the road. A sharrow isn’t a bike lane and puts you right in door zone, as you said. Beach Drive can get scary during the afternoon commute, when a ferry lets out. So, agreed, I most always ride 2 abreast.