It's easy to separate motor vehicles from bicycles and pedestrians --
just use those spikes like in gated communities. *Cyclists can slip
between the spikes or stop and step over them as can pedestrians. *A
motor vehicle will get 4 damaged tires.

Separating cyclists from pedestrians is trickier. *The first obvious
solution would be to install parallel bars like on cattle stops on
sidewalks/pavements. *A good wheelman, however, will just hit these at
an angle like he does oblique railroad tracks. *Maybe some combination
of patches of ice and grates would work but that would be expensive to
install and maintain and dangerous to pedestrians as well.

Moreover the weight of a cyclist + bicycle averages about that of a
pedestrian,

What?

What distinction are you drawing between a cyclist and a pedestrian?

More to the point, why?

both an order of magnitude less massive than a motor
vehicle. *Even more compelling a motor vehicle often represents 2
orders of magnitude more kinetic energy.

As a practical matter, is there really any reason not to reclassify
cyclists as pedestrians as far as cycling on the sidewalk/pavement is
concerned?

Yes.

A bicycle is a vehicle, not a pair of feet.

Some kids' shoes have small wheels in the heels.

It needs to be pointed out that something as successful in industry as
ball bearings is never ever found in nature. It probably has
something to do with feeding nutrients to spinning objects.

DARPA has done a lot with wheeless vehicles, things that can crawl
over rugged terrain like insects. But bad knees are proof positive
that this approach is inferior to the wheel.


Bret Cahill