Principles of roundabout traffic operation in Poland
<\/strong>The act regulating traffic regulations is the “Road Traffic Law” introduced on June 20, 1997, commonly known as the “Highway Code”. The act regulates traffic rules on public roads and in residential zones, conditions for admitting vehicles to such traffic, requirements for drivers and other road users, and rules for road traffic control. This document does not contain the term “rondo” – the colloquial name for a “roundabout intersection”.<\/p>
As the driving manual states, “A roundabout is a circular intersection where vehicle traffic moves counter-clockwise. In every case, a roundabout has an island in its central part, which is excluded from vehicle traffic, with the exception (sometimes) of tram traffic”.
A roundabout is a good solution, used mainly in urban areas; it is often used in countries with high traffic safety. Compared to other intersections, roundabouts increase capacity and reduce traffic congestion. As a result, they improve traffic flow. There are fewer points on roundabouts where accidents and collisions can occur than at other types of intersections. The design of a roundabout forces the entering driver to reduce speed and enables good visibility for road users, which increases safety.
As studies show, there are generally 5 times fewer accidents at roundabouts than at other intersections, and 2 times fewer in cities. Thanks to the use of roundabouts, the number of fatal accidents drops by over 95%. In 2007, there were 460 accidents at roundabouts, while there were 14,336 accidents at other intersections. Among these accidents, the number of fatal accidents amounted to 14 fatalities at roundabouts and 826 at other intersections.<\/p>
Purpose of developing a roundabout traffic simulation system
<\/strong>Simulation is the study of the behavior of a given system, which is the subject of the simulation, depending on specific input parameters. Changes in input parameters cause changes in the system’s output. The purpose of simulation is to build a mathematical model that links these input parameters in such a way as to obtain a specific result at the system’s output. The subject of the study does not have to exist in reality while the simulation is being conducted. Simulation can show that such an object can be created if the simulation results are positive.
The study of a given system can be carried out empirically if technical possibilities exist and the time and costs of implementation are acceptable. Otherwise, computer simulation techniques can be used to conduct the research.
There are two types of computer simulations: discrete-time simulations and continuous-time simulations. Discrete-time simulations are used to study the behavior of real and hypothetical systems. On the other hand, continuous-time simulations are for studying systems in which continuous changes dominate. In the case of roundabout traffic simulation, a discrete-time method will be used. Discrete computer simulation has many advantages, including:<\/p>
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the possibility of obtaining a lot of information about the studied system already in the design phase. Thanks to this, answers to some questions about the system can be obtained without the need to build and test it (for example, by trial and error)<\/div>
<\/li>defining the purpose of the simulation and adjusting the input parameters to it allows for studying the system’s behavior under various conditions, even those that are difficult to obtain in reality (rarely occurring), or even those that do not yet exist in reality<\/div>
<\/li>computer simulation is a process that can be easily repeated. Thanks to this property, it allows for conducting many studies at a low cost<\/div>
<\/li>the simulation time can be significantly shortened depending on the computing power of the computer<\/div>
<\/li>the flexibility of the simulation allows for conducting research on real and hypothetical systems, which enables the development of new, more effective systems<\/div>
<\/li>based on the system simulation, its utility can be determined depending on the simulation result. In the case of a negative result, the cost incurred for conducting the simulation is not as high as in the case of actual construction of the system, conducting research, and its liquidation.<\/div>
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<\/ul>Traffic simulation is a difficult area of research due to the presence of many factors that make it impossible to determine its unambiguous characteristics. The human factor also plays an important role in implementation, and it is impossible to clearly define its behavior. In vehicle traffic, there are spatio-temporal dependencies that can be determined by mathematical functions. Traffic rules have been defined, and with their help, rules can be developed according to which the traffic process will be carried out.<\/p>
For the purposes of this article, a roundabout traffic simulation system has been developed, where the input data are:<\/p>
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roundabout components: number of inlets/outlets, number of lanes on the roundabout and inlets, roundabout radius, length of inlet lanes<\/div>
<\/li>number of vehicles generated at a given inlet (weight ratio relative to other inlets)<\/div>
<\/li>number of vehicles heading to a given outlet from a specific inlet (by weight)<\/div>
<\/li>length of cars<\/div>
<\/li>speed of cars<\/div>
<\/li>right-of-way rule for road users already on the roundabout or those entering the roundabout<\/div>
<\/li>percentage of vehicles entering the roundabout directly into the outer lane.<\/div>
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<\/ul>The article comes from the journal “Logistyka” 5/2010.<\/p>
7319_Logistyka2010-III.pdf<\/a>