Here in London, we are coming to understand that the re-allocation of road space from cars to bicycles contains costs that are not apparent from the outset. It is one thing when we are dealing with little-used suburban and local streets, but quite another when the appearance of bicycles in dozens and scores forces following traffic to advance at bicycle speed. This is especially true when outraged motorists are impeded and demand that bikes share their lanes with cars and trucks, often close and frequently fast. The law in WI has always required that they take a full lane, so as not to subject this fragile traffic to the danger of being forced off the road or crushed. I have even been harassed by police in the Arboretum for not moving over to share a single lane with a police car. The secret lies in the growth of traffic. As urban housing and offices dictate the razing of 3- and 4-story houses to apartment blocks of 12 or 20 stories, even worse in cities like London, where, as 30- and 40-story buildings are increasingly to be seen, the streets will have no room into which to expand. As an engineering problem, I see no solution but the division of the space over the roads into motorized traffic at the street level and elevated promenades for pedestrians and non-motorized bikes and skates. A civilizing dent can be made by saving the sky over the sidewalks and having the light traffic as high as the third story to allow a sense of space to those using the lower level. Otherwise, in time the bicycles will push the cars and trucks off the streets entirely, though at significant peril. And if we are to find some recourse in downtown construction, we had better get building very soon. If we wait long enough, the construction alone will be very costly and more intrusive. Meanwhile, we can expect the existing roads to become increasingly crowded and dangerous, and increasingly unattractive as an engineering problem.