"Someone should do the math" - you may find that if Transit just closed and fenced off one of the existing lanes for cyclists and walkers and actually paid them to ride and walk over the bridge then it would be cheaper and more effective in terms of reducing congestion than adding on another lane.

If you are going to add a cycling and walking lane on the bridge let's just hope that its not like the design cobbled together at Greenhithe Bridge with very poor connections at each end. It was also a miracle no cyclist were killed during its construction. Their efforts todate refect the current culture at Transit - which is that cycling is fringe lunatic.