For example, adding an urban highway lane typically accommodates about 2,000
additional daily vehicle trips.
Although this reduces congestion on that roadway (at least
temporarily, until generated traffic fills the capacity), it often increases “downstream”
surface street traffic congestion, increases parking demand, requires travelers to own and
operate automobiles, and if additional vehicle travel is induced it increases accidents,
energy consumption, pollution and sprawl, all costs that could be reduced if the same
trips are made by alternative modes.