Pedestrians already have their 2nd grid of roads, it's called the sidewalk. Problem is that bikes also don't fit there, so basically they need a 3rd set of roads.
When they took down the passenger rail way back in the day, they replaced the network with hiking/biking trails.
And in the winter, you have a cross-city skiing network.
Granted, there's plenty of space around those corn fields, but something tells me that if Cedarloo can pull it off, the richer cities can, too.
Is it flat like Copenhagen?
In any case, the trails were laid over a former rail track, so the trails are very flat[1] - never steeper than 2% grade.
I'm just wondering if a better use of the street could be achieved; that doesn't have to mean cars. What about a bus + moped lane? Electric mopeds seem like a pretty good alternative for people who need something faster than a scooter, and having ridden a bicycle in Amsterdam, where mopeds could use the bicycle lane, I can tell you they don't belong there!
They use a trick: where the bus lane merges they have a traffic light. Cars have to wait for the bus -- literally -- and are only allowed to merge behind the bus. When the bus stops there are street baffles preventing the cars overtaking the bus. This way the bus has a free lane ahead. And the cars would have needed to wait in the traffic jam anyway, so why not let them wait intelligently behind buses?
Of course, at this point, you might as well use streetcars. But I think buses are still cheaper at that point.
EDIT: Nevermind, this is it: https://news.ycombinator.com/item?id=17034100
Pics: https://www.google.co.uk/search?q=london+bus+lanes&source=ln...: