Maybe I'm missing something here or just unsympathetic but if someone can get on and off a boat and from the end of a dock (on land) to a store or restaurant , it doesn't seem like a handicapped dock space would make much difference
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Automotive handicapped spots are wider to accomodate vans with lift gates for wheel chairs. The only one I've ever seen like that was a flat bowed john boat with an aluminum ramp and it had to be nosed into the dock. and not parallel.