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An accident? Construction work? A bottleneck? No, just too much traffic
IOP
PR14
Tue, 4 March 2008
A new study from a Japanese research group explains why we’re occasionally caught in traffic jams for no visible reason. The real origin of traffic jams often has nothing to do with obvious obstructions such as accidents or construction work but is simply the result of there being too many cars on the road.
The research, published today, Tuesday, 4 March, in the New Journal of Physics, shows how model patterns, normally used to understand the movement of many-particle systems, have been applied to real-life moving traffic. The research shows that even tiny fluctuations in car-road density cause a chain reaction which can lead to a jam.
The research found that tiny fluctuations in speed, always existing when drivers want to keep appropriate headway space, have a cumulative effect. Once traffic reaches a critical density, the cumulative effect of gentle braking rushes back over drivers like a wave and leads to a standstill.
The researchers in Japan used a circular track with a circumference of 230m. They put 22 cars on the road and asked the drivers to go steadily at 30km/h around the track. While the flow was initially free, the effect of a driver altering his speed reverberated around the track and led to brief standstills.
Yuki Sugiyama, physicist from NagoyaUniversity, said, “Although the emerging jam in our experiment is small, its behaviour is not different from large ones on highways. When a large number of vehicles, beyond the road capacity, are successively injected into the road, the density exceeds the critical value and the free flow state becomes unstable.”
The researchers will be advancing their research by using larger roads and more vehicles to further test their findings.
The research suggests that it might be possible to estimate critical density of roads, making it possible to build roads fit for the number of drivers needing use of it or, on for example toll roads, only allowing the right number of cars access to the road to stop mid-flow traffic jams.
ENDS
Please credit the Institute of Physics’ New Journal of Physics for this news story
Notes to editors:
Contact
1. For further information or a full draft of the journal paper, contact IOP Press Officer, Joe Winters:
Tel: 020 7470 4815
Mobile: 07946 321473
E-mail: joseph.winters@iop.org
Traffic jam without bottleneck – Experimental evidence for the physical mechanism of the formation of a jam
2. The paper "Traffic jam without bottleneck – Experimental evidence for the physical mechanism of the formation of a jam" (2008 New J. Phys. 10 033001) is available online from Tuesday, March 4, at http://stacks.iop.org/NJP/10/033001.
New Journal of Physics
3. New Journal of Physics, co-owned by the Institute of Physics and German Physical Society, is an electronic-only, open-access journal publishing original research from across the whole of physics. All articles are permanently free to read at http://www.njp.org.
Institute of Physics
4. The Institute of Physics is a scientific membership organisation devoted to increasing the understanding and application of physics. It has an extensive worldwide membership (currently around 34 000) and is a leading communicator of physics with all audiences from specialists through government to the general public. Its publishing company, IOP Publishing, is a world leader in scientific publishing and the electronic dissemination of physics. Go to www.iop.org.
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