Running on road vs sidewalk

It depends, most times I run on the road (bike lane) its because the sidewalk in those areas are uneven, cracked or poorly lit.  When I'm running early in the morning or at night I avoid those areas so I don't twist an ankle or trip and bash my head open.

I want to annoy the cyclists.

Its about density, running on softer surfaces is better for joints and stability muscles.

asphalt is 721 kg/cu.m

concrete is 2243 kg/cu.m

I run on the road since i do not have the option of sidewalks, there are few and far between, i will use them if i am on a busy road and they are available, i also remember reading an article way back about running on the blacktop of the road was better for your knees and feet than running on the cement of the sidewalks.. not sure if that is a true statement but i did read it once somewhere...

x2.  I also change my gait when running on the sidewalk in order not to trip on the uneven concrete.  

When running on the road should you run with or against traffic?  

This mostly.  Along with having to cross driveways etc that are all graded differently which tends to cause issues for me biomechanically.  I do choose the sidewalk on roads that are too busy or if the road is too cambered which causes the same issues as above. 

Ride with

Run against

I run mostly in neighborhoods, and stay on the roads instead of the sidewalks to avoid the many trees and bushes that crowd the sidewalks. I have scraped my head and my back bad on low hanging trees.

X2 on running with some sort of light when it is dark, both to see and to be seen. 

I also run a lot with my dog, and the sidewalks are often too narrow, and it saves us being surprised by dogs behind fences.

just thought I'd throw a few more reasons out there.

This, plus I dont understand why people park in their driveways blocking the sidewalk.  There is usually plenty of room to pull up a few feet and not block the sidewalks.  For these reasons,  I gave up running on sidewalks long ago.

My knees ache every time I see someone run on a sidewalk.  Proven the worst surface you can run on.  

I only run on sidewalks if there is no other choice.

His knees?

Depends, I'll choose whatever is the smoothest and least crowded(dodging SF photo taking, stroller wielding packs of tourists can be a nightmare) usually the road; but if that has a big camber, potholes, or a lot of parked cars that put me out in the path of drivers then I'll move it up on the sidewalk.  Most of my falls (there have been many) have been on the sidewalk.  It seems to jump up and trip me from out of no where 

When I first started running concrete seemed very unforgiving but I really don't notice a difference anymore.  But then again, most of my neighborhood/sidewalk runs are pretty short (under 5mi).