TO UNDERSTAND WHY urban planners like bicycles, stand on a section of Saint Denis Street in Montreal and count the vehicles going by. On a sunny Thursday over a ten-minute period at rush hour, your correspondent counted 132 bicycles (at least a half dozen of which had children on the back) flowing one way. In the adjacent—and much wider—automobile lane 82 cars (almost all carrying just their driver) and one city bus moved by in a bumper-to-bumper crawl.