For decades, economists and other transportation thinkers have advocated imposing tolls that vary with congestion levels on roadways. Simply put, the more congestion, the higher the toll, until the congestion goes away.
To many people, this sounds like a scheme by mustache-twirling bureaucrats and their academic apologists to fleece drivers out of their hard-earned cash. Why should drivers have to pay to use roads their tax dollars have already paid for? Won’t the remaining free roads be swamped as drivers are forced off the tolled roads? Won’t the working-class and poor be the victims here, as the tolled routes turn into “Lexus lanes”? ...
[Variable] tolling is an excellent public policy. Here’s why: the basic economic theory is that when you give out something valuable — in this case, road space — for less than its true value, shortages result.
Ultimately, there’s no free lunch; instead of paying with money, you pay with the effort and time needed to acquire the good. Think of Soviet shoppers spending their lives in endless queues to purchase artificially low-priced but exceedingly scarce goods. Then think of Americans who can fulfill nearly any consumerist fantasy quickly but at a monetary cost. Free but congested roads have left us shivering on the streets of Moscow.
--Eric A. Morris, Freakonomics blog, on the virtues of congestion tolls