The only place I habitually bailed off the road in my commute was on a steeply climbing, completely shoulderless 4 lane arterial with major downtown traffic. I felt it was asking too much of other traffic to hold them to my 4mph speed while they were trapped by passing traffic in the inner lane and unable to pass me. In addition, there was the risk of getting rear ended just past the top of the hill by traffic that wouldn't see me in time due to the steepness of the hill. I took to the sidewalk for 1/4 mile, but have since found an alternate route that solved the problem.