Greenberg and Lethco point out that continual efforts to increase capacity for cars has only resulted in more congestion. The solution, they suggest, is to treat all modes as complementary and not mutually exclusive: most of us are, at various times, pedestrians, cyclists, transit users and car drivers. Ironically, the more we invest in non-auto infrastructure, the better the driving conditions become:
"Every additional trip we take on foot, on a bicycle or by public transit frees up significant space for drivers, since the 'footprints' of these other modes are so much smaller. The cyclist beside you is not the car in front of you; the bicycle locked to a ring at curbside means one less parking space is taken. Driver, cyclist and pedestrian are complementary rather than mutually exclusive categories. Most of us are all of these at different times. What's crucial is the proportion of time we use each mode, and creating communities where the car is needed for only certain types of trips. For other trips, we can make more efficient choices.
If we decide we want our system to be more efficient, we must...ensure it has the attributes that make the more efficient choices the attractive ones – and that comes through land use, system design, pricing and skillful urban design."