Traffic jams are usually caused because there must be an accident, some type of serious incident up ahead just out of sight, the roads are icey and dangerous, or its rush hour. For more information about this question go to Google.com and type in ''What causes traffic jams?". Most often, they are caused by idiots - those who drive too fast always end up riding up on those driving the speed limit in front of them, recklessly weaving in and out of lanes because they feel the road is their own personal playground. You get what's known as rush hour when you factor in the same number of roads and lights and detours and closed lanes from construction with how overpopulated the area is.
You can't understand it -- how can a five-lane highway become so packed? It feels as if every car in the city has joined you on the highway at the same time. Traffic creeps forward at a snail's pace, when it moves at all. You're forced to waste time, gas andmoney. What causes this? As the first car stops, the following cars must also stop. Even when the first car begins to move again, additional approaching cars have to stop farther down the road, and the congested area travels backward in a wave until traffic is light enough for it to dissipate. Assuming construction, accidents, and stalled vehicles aren't to blame, it's likely due to more cars entering the highway than leaving it. As more cars enter a crowded road, drivers have to use their brakes to avoid collisions, creating a traffic wave. A traffic wave occurs when cars slow down, and the slowing trend continues backward -- like a domino effect. As long as there are more cars approaching from behind, the traffic congestion travels in a wave. In general, you can divide up the contributors of traffic into two broad areas: network overload and traffic disturbances. Network overload
If there are highways or surface streets that suffer from heavy traffic congestion, no matter what the actual road conditions might be, they fall into the category of network overload. These are the bottlenecks and traffic snarls where demand always outweighs capacity. As space opens up ahead of your car, you can accelerate and escape the congestion. The person behind you can accelerate a few moments later, and the person behind them a few moments after that. The congestion doesn't immediately clear up -- it continues to shift slowly back down the highway. Congestion can clear if traffic becomes light enough to stop the traffic-wave effect. Traffic disturbances
Accidents and breakdowns, road construction and repair, and harsh weather conditions are all considered traffic disturbances. You can't always predict where these disturbances will occur, but they still heavily impact traffic flow. It's easy to imagine construction, an accident, or a cop giving a traffic ticket causing congestion -- drivers slow down either to change lanes or engage in a bit of rubbernecking as they try to see what happened. Road work might shut down one or more lanes, requiring drivers to shift over into open but crowded lanes. Bad weather might cause some drivers to maintain a slower driving speed out of concern for safety. According to the 2007 Urban Mobility Report from the Texas Transportation Institute, traffic incidents account for between 52 and 58 percent of the delays motorists experience [source: TTI]. In the next section, we'll learn about cities and highway traffic.
Many cities, like Los Angeles, have sophisticated traffic communications systems that alert drivers to changing conditions on the road, giving them time to decide what to do. Several cities have invested millions of dollars so that road crews can rapidly travel to trouble spots. There are a few ways cities can address highway congestion:
* Ramp metering - cars are only allowed to enter the highway at timed intervals. This is done by placing a light similar to a traffic signal at the end of the ramp....