The factors behind traffic congestion. Traffic congestion occurs when the number of cars on the road exceeds the capacity of that road. While rapid growth — particularly in outlying suburban areas — has contributed to long rush hour commutes, much of the increase in traffic is due to our over-reliance on cars.
A recent nationwide study by the Surface Transportation Policy Project showed that of the major factors contributing to increased congestion — the largest, accounting for 37 percent, was the increasing number of car trips in people's daily lives. Trips occurring because of new development accounted for only about 16 percent of the increase in traffic.
When new low-density construction takes place at the urban fringe automobiles are the only viable form of transportation and every activity — going to school, going to work, going to soccer practice, going out to eat, going to the movie, buying a quart of milk or a newspaper — requires getting in the car and driving somewhere. These extra car trips caused by suburban-style development have a greater impact on traffic, particularly on collector roads, than building apartments in an already built up area.