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The width of an auxiliary lane should be equal to the through lanes. Where auxiliary lanes are provided along freeway main lanes, the adjacent shoulder should desirably be 2.4 to 3.6m [8 to 12 ft] in width, with a 1.8m [6 ft] wide shoulder being the minimum considered.
I follow your logic here, except for the instability of a bicycle requiring 10- to 12-foot wide lanes. I think 6 feet is plenty wide for a single bike. Also consider that when a group of cyclists control a lane, they naturally move into a two-abreast arrangement. And they can ride this way safely.