Oh. No. The bridge clearance on the LI parkways was _very definitely_ intentional, but really aimed at preventing them from being used by commercial truck traffic rather than busses. Local sources for it are legion and predate Caro's book by at least a decade. That's also the reason for the tight turns at exits. A car or minibus can usually negotiate those without difficulty (assuming the driver is paying attention), but they're impossible for tractor-trailers.