bikingshearer 

Okay, I mispoke. eastbound approach (San Rafeal/San Quentin) is three lanes. The lower (eastbound) direction of the bridge is two or three lanes, depending on the day and time, controlled by lights but with no physical barrier. The westbound approach (Richmond side) narrows from four lanes to three about a mile and a half before the toll plaza and then to two lanes plus the cordoned-off bike lane on the bridge itself immediately after the toll plaza.

To be clear, no lane barriers are moved - ever. The bike lane on the upper (westbound) level is for bikes going both ways - pedestrians, too, although not many of those. The barrier separating bikes from westbound cars is stationary. The only lane changes are in the eastbound direction/lower deck, controlled solely by lights (which are sometime ignored), and bikes are never on the lower deck.

I do not know why the upper deck/westbound direction was chosen for the bike lane. It certainly makes for a more pleasant biking experience than being on the lower deck, which feels a lot like a tunnel. It is significantly further from the east end of the bridge back to I-80 than from the west end of the bridge back to US 101. which means it takes a much bigger backup westbound to back onto I-80 than for an eastbound backup onto US 101. (Both I-80 and US 101 are major traffic arteries at all times, especially commute times.) That may have had something to do with choosing to put the bike lane on the westbound upper deck.

I hope this better explains the lay-out.

As for removing the bike lane, there is another player not mentioned so far - the MTC (Metropolitan Transportation Commission. It's a regional governmental agency that has great deal to say about where traffic and transit money from the state and federal governments goes in the Bay Area. In the recent past, the MTC has been very pro-bike-lane on the San Rafael Bridge. Indeed, the bike lane was added mainly because the MTC refused to approve continued funding for something or other Marin County mucky-mucks wanted unless the bike lane went in. I do not know whether such sentiments still prevail on the MTC, but I would not be surprised if they did. The MTC has pretty much always seen itself as the regional-focused grown-up keeping the various local government children from getting away with temper tantrums. With its power of the purse, the MTC most likely will, as a practical matter, have the final say as to whether the bike lane stays or goes. My guess is it will stay.