Traffic waves, which are also called stop waves, ghost jams, traffic snakes or traffic shocks, are traveling disturbances in the distribution of cars on a
highway
A highway is any public or private road or other public way on land. It includes not just major roads, but also other public roads and rights of way. In the United States, it is also used as an equivalent term to controlled-access highway, or ...
. Traffic waves travel backwards relative to the cars themselves. Relative to a fixed spot on the road the wave can move with, or against the traffic, or even be stationary (when the wave moves away from the traffic with exactly the same speed as the traffic). Traffic waves are a type of
traffic jam. A deeper understanding of traffic waves is a goal of the physical study of
traffic flow
In transportation engineering, traffic flow is the study of interactions between travellers (including pedestrians, cyclists, drivers, and their vehicles) and infrastructure (including highways, signage, and traffic control devices), with the ai ...
, in which traffic itself can often be seen using techniques similar to those used in
fluid dynamics
In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in motion ...
. It is related to the
accordion effect.
Mitigation
It has been said
[Traffic Wave Experiments](_blank)
William J. Beaty, 1998 that by knowing how traffic waves are created, drivers can sometimes reduce their effects by increasing vehicle
headway
Headway is the distance or duration between vehicles in a transit system. The ''minimum headway'' is the shortest such distance or time achievable by a system without a reduction in the speed of vehicles. The precise definition varies depending on ...
s and reducing the use of
brake
A brake is a machine, mechanical device that inhibits motion by absorbing energy from a moving system. It is used for Acceleration, slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of ...
s, ultimately alleviating
traffic congestion
Traffic congestion is a condition in transport that is characterized by slower speeds, longer trip times, and increased vehicular queueing. Traffic congestion on urban road networks has increased substantially since the 1950s, resulting in m ...
for everyone in the area.
However, in other models, increasing headway leads to diminishing the capacity of the travel lanes, increasing the congestion; however, disputed by acknowledging that similar principles apply to herding sheep through gates, and that in such a case, via human intervention,
soliton
In mathematics and physics, a soliton is a nonlinear, self-reinforcing, localized wave packet that is , in that it preserves its shape while propagating freely, at constant velocity, and recovers it even after collisions with other such local ...
s are diminished simply by slapping "stuck sheep" and holding back aggressive sheep. In funnelling sheep through gates it can be determined how much intervention is needed to curb bottlenecks. Similar principles can be applied to human traffic streams, where, if each individual had the knowledge of final destination and complete route planning, then traversal along a route would be done so with the full knowledge that any abrupt change from any itinerary causes delays for those about to traverse the same route.
History
The earliest theoretical model of traffic shock waves was offered by
Lighthill and Whitham in 1955. The following year
Paul Richards independently published a similar model. Both papers were based on fluid dynamics and the model is known as the Lighthill-Whitham-Richards model.
[Kerner, Boris S., ''The Physics of Traffic'', Springer, 2012 .]
See also
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Autonomous cruise control system
*
Fundamental diagram of traffic flow
*
Green wave
*
Road traffic control
*
Rule 184
*
Wavelength
In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats.
In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...
*
Shock wave
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...
*
Standing wave
In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect t ...
References
External links
Traffic Jam Recreated for the First Time - New Scientist original research page and YouTube video of spontaneous traffic wave
Traffic Wave - Science Hobbyist
{{DEFAULTSORT:Traffic Wave
Waves
Road transport
Fluid dynamics