Why? The Logical Underpinnings of Congestion Pricing (a brief tutorial)

                                    
                       
The text imprinted in the graphic at right distills the essence of the traffic "problem": although drivers are quite cognizant of the impact of traffic on the time their own trip will take, they're largely unaware of the extent to which their trips slow down traffic at large. Indeed, they have no need to ponder the "time costs" their trips impose on others, since they are not charged for them.              
                       
                       
                       
                       
In light or even moderate traffic conditions, those time costs are generally modest -- my trip hardly slows down traffic, and there aren't enough other folks on the road for any delays I cause to add to much. But in the heavy traffic conditions that typify congested NYC roads -- especially in the Manhattan Central Business District and on the approaches to it -- those costs can be substantial.                       
                       
                       
                       
                       
In another part of this spreadsheet, the 'Delay Costs' page (tab), we estimate that a typical round-trip into and out of the CBD, from a distance of around 18 miles, slows down other road users -- cars, trucks, cabs, buses -- by an aggregate total of 3 to 4 hours. Yet the would-be driver deciding whether to make that car trip has no reason to factor those prospective delays into her or his decision.                       
                       
                       
                       
                       
Congestion pricing, or 'traffic pricing' broadly, is a way to 'close this loop.' It does so through toll charges that incentivize prospective trip-takers to take into account the delays they will impose on others. This 'cost-internalization' will lead some trip-takers -- just how many depends on the toll level -- to switch their trips to different modes (transit, carpool, bike), to other destinations, or to other times of the day or week. The thinning of the traffic stream that results will improve traffic flow significantly (provided the toll is more than a token dollar or two). We estimate that for the Move NY - Gridlock Sam Fair Plan, average speeds of car travel within the Manhattan Central Business District will increase by 21%. Though gains in speeds outside the CBD (on the approaches) will be proportionately smaller, traffic volumes there are so great that the aggregate hours saved on trips that use the approaches but don't cross into the CBD (and thus won't pay the toll) are predicted to exceed the total time savings on trips going into or through the CBD.                       
                       
                       
                       
                       
                       
                       
                       
                       
                       
To see the time savings, go to the 'Results' page (it's several pages 'down' from this one). Our model estimates that, over the course of a year, the Move NY - Gridlock Sam Fair Plan will save CBD trip-takers a total of 45 million hours they will otherwise spend sitting in traffic, while another 58 million hours will be saved by drivers on trips that use the approaches but don't enter the CBD. The monetary value of this saved time is around 2 billion dollars a year, as can be seen elsewhere on that page.                       
                       
                       
                       
                       
The other big plus from congestion pricing in New York City will be generation of a large and reliable revenue stream that can be used to improve the city and region's transportation infrastructure. We estimate that after paying for toll collection and other system costs, the Move NY - Gridlock Sam Fair Plan will be able to provide $1,57 billion to invest *each year* in improved subways, buses, rail and roads. These expenditures will revitalize mass transit, saving transit users an estimated 88 million hours in travel time annually and drawing *additional* car trips off of the roads and into transit (thus contributing to the travel time savings noted in the prior paragraph). The improvements to the roads will generate further road travel time savings that we haven't quantified here. 

Fuente: CONCATENER  ( 07/03/2013)