In part it depends on what conflicts the sidewalk presents you with. At every intersection, even every driveway, you are at greater risk of colliding with cars if you are on the sidewalk. Obviously you are a silent but deadly hazard to pedestrians as well. They will wander into your path, step out from behind screening objects, freeze when they see you coming and then step to the side just as you try to go around them, let their dogs and leashes block your path etc. If the sidewalks have long uninterrupted stretches, good visibility and no pedestrians you may be fine, but if they have pedestrians, intersections and obstructed views you're twice as likely to have an accident as on the road.