You can think of rush-hour traffic as a fairly straightforward problem of supply and demand. The supply is the capacity on city buses, trains, and roads. The demand is the share of metro area commuters who want to ride transit or drive cars. Congestion at the morning and evening peaks is a sign of demand overwhelming supply: too many commuters trying to use buses and trains and roads at the same time.
link para reportagem: http://www.citylab.com/commute/2014/05/using-insights-and-incentives-end-rush-hour/9101/