As usual, sensible advice from Michael W. Pballingal, there are a number of reasons riding on the footpath/sidewalk is more dangerous. For one thing, only about 3% of bike/car collisions are caused by cyclist being hit from behind. The biggest danger comes at intersections. This is multiplied on the footpath because drivers are less likely to watch the footpath as they come out of their driveway (as a pedestrian, I know).

I usually ride as far to the left (the right for those in the US) as is safely possible. Sometimes I take the lane if I want to avoid broken glass or something, at which point I make a handsignal in advance of my intentions.