An overabundance of free or low-rate parking can have several effects.  First, it may promote commuters to drive single-occupant vehicles rather than ridesharing or taking transit.  This may lead to increased congestion on the highway network.  It hinders short-term parking needed for commercial areas. 

Parking Pricing is a strategy to limit the parking demand which in turn may reduce single occupancy travel.  Rates charged for parking vary by demand.  Typically, rates increase as the demand increases.  Often parking pricing, in combination with reduced parking requirements for development, shared parking and other techniques may be implemented as a TDM strategy (to reduce vehicle traffic in an area) and ways to maximize developable land.