It begins to display dynamic instability, meaning small disturbances are amplified. The instability is a positive feedback loop. Above the critical density, any additional vehicle reduces the number of cars per second passing through a given point on the road. This in turn means it takes longer for a local pileup to move out of a section of the road, increasing vehicle density even more, which eventually adds up to stop-and-go traffic.
Drivers tend not to realize they need to break far in advance of a traffic jam, which means they end up having to brake harder to avoid a collision. This strengthens the wave of braking from vehicle to vehicle.
Then, they have to brake again, eventually producing another feedback loop that causes more stop-and-go traffic. As it turns out, a few different groups of researchers have been using mathematical calculations and real-world experiments to try answering this question. And they think they have the answer. They also have suggestions on how to stop these jams.
If there are enough cars on a highway, any minor disruptions to the flow of traffic can cause a self-reinforcing chain reaction: one car brakes slightly, and the ones behind it brake just a bit more to avoid hitting it, with the braking eventually amplifying until it produces a wave of stopped or slowed traffic. Even when cars leave this traffic wave, though, the wave itself doesn't disappear: it gradually drifts backward, against the direction of traffic.
He and others developed the concept of these waves which they call jamitons, because they're analogous to waves in physics called solitons using computer algorithms that simulate driving behavior:. Japanese researchers have also conducted real-world experiments that come to the same conclusion. In one, they instructed 22 drivers to drive at the same speed Inevitably, traffic waves formed:. In one sense, it seems reasonable to blame these phantom traffic jams on individual drivers.
The models indicate that these jams are more likely to form when people drive as fast as possible, then finally brake when necessary to avoid hitting the car in front of them, triggering a chain reaction. Another way to think of it, says Berthold Horn — an MIT computer scientist who's worked on the same topic — is to try driving so that you stay halfway between the car in front of you and the one behind you.
This will lead to you avoid sudden braking when possible. On the other hand, this sort of behavioral change doesn't totally eliminate phantom traffic jams — it merely makes them less likely to form specifically, it means that a higher density of cars on the road is required for traffic waves to develop. But if there are enough cars on the road, even if people anticipate approaching traffic to the best of their abilities, phantom traffic jams will form.
These jams, in essence, emerge whenever you have enough humans driving cars on a highway. So the only real way to eliminate them probably involves handing the wheel over to something other than a human driver. A prototype of Google's self-driving car. The straighter and smoother a road is, the less likely the jams are to form, since it means drivers won't be doing as much sudden braking. Do we then destroy them or turn the street into pedestrian and bike malls, banning automobile traffic entirely?
Or has anyone not thought that far ahead? Most likely the choice would be to destroy the trees or severely prune them unless by then we are all telecommuting or traveling with our rocket jet packs. In that case I would favor pedestrian malls everywhere. The truth is that traffic congestion is caused by multiple causes and here they are not in the order of importance. These can be any of the following:. Sometimes it is the driver who insists on driving his car even if mass transit makes more sense.
But that is more the exception than the rule. People usually tend to do what makes the most sense for them. Sometimes DOT is to blame by purposely making the signals out of sync turning your signal green and the following red at the same time forcing you to just miss it. The DOT believes this will improve safety, especially around school zones, by forcing everyone to start and stop.
However, in reality, all it does is increase air pollution, waste gas and time, and cause cars to illegally speed up just catch two green signals in a row, which would be otherwise impossible, thereby increasing danger not reducing it. There is probably nothing more frustrating to a driver than to take 10 or 15 minutes just to travel 10 short blocks without any traffic, but because of ill-timed signals, increasing frustration and possibly road rage.
It also makes no sense for the traffic signals to force you to slow down around schools at a. Sometimes, it is the MTA that is not doing all it should do to improve local bus service such as not providing extra buses to beaches when needed , or operating too many buses not in service at the same time that overcrowded buses are bypassing stops, thus encouraging automobiles and dollar vans to create further congestion.
If you want drivers to leave their car at home, then give them better options. Give them a direct bus route if a subway cannot be justified, or at least a trip that can be made by taking two bus routes or even three.
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