Traffic congestion

From Free net encyclopedia

Traffic congestion describes a condition in which vehicle speeds are reduced below normal, increasing drive times, and vehicle queueing occurs. It occurs only when the demand is greater than the roadway's capacity. These conditions are also more frustrating for drivers (see road rage), and automobile accidents may be more frequent. However, congestion reduces speed which is a primary factor contributing to accidents. So, traffic congestion can reduce the number and severity of accidents. Furthermore, vehicles burn unnecessary fuel when stuck at idle. A period of extreme traffic congestion is known as a traffic jam.

Traffic engineers sometimes apply the rules of Fluid Dynamics to traffic flow, likening it to the flow of a fluid in a pipe. Traffic jam simulations have shown that in heavy but free flowing traffic, jams can arise spontaneosly, triggered by minor events such as an abrupt steering maneuvre by a single motorist. Such a situation is likened to the freezing of supercooled fluid by traffic scientists Template:Ref.

Congested roads are an example of the tragedy of the commons. Because roads in most places are free at the point of usage, there is no financial incentive for drivers not to over-utilize them, up to the point where traffic collapses into a jam. Privatization of highways and road pricing are measures that can prevent congestion through economic incentives.

Economist Anthony Downs, in his books Stuck in Traffic (1992) and Still Stuck in Traffic (2004), offers a dissenting view: rush hour traffic congestion is inevitable because of the benefits of having a relatively standard work day. In a market economy, goods can be allocated either by pricing (ability to pay) or by queueing (first-come first-serve); congestion is an example of the latter. Instead of the traffic engineer's solution of making a "pipe" large enough to accommodate the total demand for peak-hour vehicle travel, either by widening roadways or increasing "flow pressure" via automated highway systems, Downs advocates greater use of road pricing to reduce congestion, in turn plowing the revenues generated therefrom into public transportation projects.

Template:Globalize

1 Traffic congestion in the United States
2 Classification
3 Attempts to alleviate traffic congestion
4 References
5 See also
6 External links

[edit]

Traffic congestion in the United States

Image:Santamonicafreewaynearrobertson.jpg

In the United States, construction of new highway capacity has not kept pace with increases in population and car use and the resulting increase in demand for highway travel. Between 1980 and 1999, the total length of highways as measured by miles increased by only 1.5 percent, while the total number of miles of vehicle travel increased by 76 percent.

The Texas Transportation Institute estimates that in 2000 the 75 largest metropolitan areas experienced 3.6 billion vehicle-hours of delay, resulting in 5.7 billion US gallons (21.6 billion liters) in wasted fuel and $67.5 billion in lost productivity. Traffic congestion is increasing in major cities, and delays are becoming more frequent in smaller cities and rural areas.

The four areas in the United States with the highest levels of traffic congestion in order are: [1]

Due to dramatic population increases, San Diego and Las Vegas have seen their congestion levels increase by more than 50 percent since 1982.

[edit]

Classification

The U.S. Department of Transportation uses the following scale, based on lane occupancy, to classify traffic congestion:

35% or higher: Stop and Go
22% - 35%: Heavy
15% - 22%: Moderate
0-15%: Wide Open

[edit]

Attempts to alleviate traffic congestion

Image:Auto stoped highway.JPG

Improvements of junctions.
Broadcasting road conditions via traffic reports.
Building new roads and widening of existing ones (this practice is criticised by proponents of the induced demand hypothesis)
Road pricing, or tolls, such as the London congestion charge, a fee levied on vehicle drivers entering the centre of the city
Cheaper and better public transport offered by the local or provincial government, see Public Transport Funding
Setting of school opening times to avoid problems associated with the school run
High-occupancy vehicle lanes or "carpool lanes"
Quotas on the number of vehicles on the road. Examples are the fairly successful "cap and trade" method used in Singapore [2] and number plate restrictions on certain days of the week, as practiced in Athens and Mexico City.
Traffic management and prevention of accidents
Doing away with turns across oncoming traffic at crossroads with traffic lights, which reduces the time needed to go through such crossroads.