“An iron law of economics states that demand always expands beyond the supply of free goods to cause queues. There is no better illustration of this law than the traffic congestion in virtually every major city and also in many smaller cities that has resulted from allowing city roads to be used without paying any fees…The optimal way to induce drivers to take account of the congestion they cause to others is to charge them fees for driving during congested periods that would vary with the degree of the congestion. So these fees would be higher during rush hours than during other hours of the day, and they would be lower on weekends when traffic is generally lighter than on weekdays. Fees should be greater when it is raining or snowing since congestion is greater with bad weather, in part because driving is slowed down by the weather, and in part because more people decide to drive rather than walk or take public transportation when it rains”. –Gary Becker, Nobel Laureate in economics, writing in the Becker Posner Blog