Parallels between bikes on the sidewalk and cars on the road

There has been an unfortunate trend of pedestrian injuries from collisions with bicycles. Of course, many people have called for more enforcement and penalties for biking on the sidewalk, which is illegal in most cases. And I can agree with the sentiment behind most of this: that bikes, being the heavier and faster mode of transportation, have extra responsibility to not harm pedestrians. But what if you extend this concept from the sidewalk to the road, where bikes should be.

(The parallels aren't perfect between the road and the sidewalk, but some rough guesses show that while a bike has 20 times the kinetic energy of a pedestrian, a car has 50 times for energy than a bike. And this energy is in the form of a hard metal shell.)

This parallel leads me to a couple questions:

If you can't bike on a sidewalk because very occasionally a collision occurs that injures or kills a pedestrian, why can cars use the same road as me on my bike?

Why can a bike share a Multi-Use Pathway (MUP) with pedestrians but not a sidewalk? In Calgary, these occasionally have separate paths for bikes and pedestrians, but are primarily shared. There have been collisions on these as well.

For the Calgarians, would you bike on Memorial Drive while the north side of the Bow MUP is closed? Would you share the lane with this Ford or take the lane? http://g.co/maps/pqbqm

Maybe the inevitable conclusion to this is that bikes need separated bike lanes. But those are going to be a long time coming, and they will never be everywhere, at least not in Calgary.

Spreadsheets with my assumptions for the relative energies:http://goo.gl/dFqXz

Blog about bike/pedestrian conflicts in Calgary:http://blogs.calgaryherald.com/2011/09/06/construction-pushing-cyclists-onto-the-sidewalk-on-calgarys-showcase-pathway-says-neighbour/

Crossposted to http://www.bikecalgary.org/node/2972