Professor Peter Furth has ridden his bicycle to work at Northeastern University each day for the past six years. The two-mile trip through the Boston suburb of Brookline, Massachusetts, is usually without incident. Furth's journey is worlds apart from his former Boston commute, which for 13 years was a battle with drivers who wanted him on the sidewalk. "I've had motorists that drive a couple of inches from my elbow, trying to scare me," he said. Furth would catch up with drivers at stoplights and ask them whether they knew how close they'd come to hitting him. Invariably, they would...