"... lack of protection ... lack of shade, cars blowing past ... pollution..."
That's the best you can do? Pedestrians need more shade? Pollution is a problem unique to people walking? Cars blowing past are a factor on any sidewalk, good or bad.
Maybe Denver can do the following: place construction-type concrete barriers at all curbs, let Christo create some canopies, move all sidewalks 10' away from the streets, and offer free filter masks to anyone who can walk to the distribution center.