Traffic waves, 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 is used for major roads, but also includes other public roads and public tracks. In some areas of the United States, it is used as an equivalent term to controlled-access ...
. 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
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. When traffic de ...
. A deeper understanding of traffic waves is a goal of the physical study of
traffic flow
In mathematics and 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 devi ...
, in which traffic itself can often be seen using techniques similar to those used in
fluid dynamics
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) an ...
. It is related to the
accordion effect
In physics, the accordion effect, also known as the slinky effect, concertina effect, elastic band effect, and string instability, occurs when fluctuations in the motion of a travelling body causes disruptions in the flow of elements following it. ...
.
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 measured in space or time. The ''minimum headway'' is the shortest such distance or time achievable by a system without a reduction in the speed of vehicles. The precise defi ...
s and reducing the use of
brake
A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction.
Background ...
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. When traffic de ...
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 or solitary wave is a self-reinforcing wave packet that maintains its shape while it propagates at a constant velocity. Solitons are caused by a cancellation of nonlinear and dispersive effects in the medium ...
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
*
Autonomous cruise control system
Adaptive cruise control (ACC) is an available cruise control advanced driver-assistance system for road vehicles that automatically adjusts the vehicle speed to maintain a safe distance from vehicles ahead. As of 2019, it is also called by 20 u ...
*
Fundamental diagram of traffic flow
The fundamental diagram of traffic flow is a diagram that gives a relation between road traffic flux (vehicles/hour) and the traffic density (vehicles/km). A macroscopic traffic model involving traffic flux, traffic density and velocity forms the ...
*
Green wave
A green wave occurs when a series of traffic lights (usually three or more) are coordinated to allow continuous traffic flow over several intersections in one main direction.
Any vehicle traveling along with the green wave (at an approximate spee ...
*
Road traffic control
: ''For the road traffic science, see various articles under Road traffic management.''
Road traffic control involves directing vehicular and pedestrian traffic around a construction zone, accident or other road disruption, thus ensuring the safety ...
*
Rule 184
Rule 184 is a one-dimensional binary cellular automaton rule, notable for solving the majority problem as well as for its ability to simultaneously describe several, seemingly quite different, particle systems:
* Rule 184 can be used as a simpl ...
*
Wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
*
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 med ...
*
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 ...
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
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Waves
Road transport
Fluid dynamics