Micro-simulation models

Micro-simulation‎models‎(also‎named‎Microscopic)‎are‎defined‎as‎“Micro-simulation models have the ability to model each individual vehicle behaviour within a network. In theory, such models‎ provide‎ a‎ better,‎ and‎ „purer’, representation of actual driver behaviour and network performance” [173] and [176].

Another reference has defined the micro-simulation‎ models‎ as‎ “They are a powerful communications tool because they are able to present its outputs as a real-time visual display”‎ [177]. It describes the interaction among drivers, vehicles and roadway environment [178]. This implies modelling the actions, e.g. acceleration and decelerations and lane changes, of each driver in response to the traffic conditions [161].

These models deal with an individual vehicle movement within the traffic system, its travel time, speed, and how the driver is moving.

The potential of microscopic models is they are able to exercise power on the individual vehicles movements in the traffic stream as they consider car-following models [68].

Historically, few examples of micro-simulation in regional evacuation analysis are reviewed due to difficulties of modelling the movement and interaction of a large number of autonomous vehicles. This is because of computational burden. In recent years, this limitations have been greatly decreased (if not eliminated) by increases in computational power and advancements in software engineering [179].

Microscopic models have a wide range of advantages. We summarized them in bullets below:

 Micro-simulation models are very useful where the increasing system complexity and uncertainty can be involved in the operation of the urban traffic networks. However, the concern is often expressed regarding misuse of micro-simulation. The response to a survey of micro-simulation‎ model‎ users‎ was‎ summarized‎ as‎ “Micro-

simulation is useful but dangerous”‎[180].

 Many important factors are considered to extend the use of traffic micro simulation models, illustrate the transport network and their operation in significant detail.

 The microscopic models are based on some traffic factors which have the ability to manage the movement of individual vehicles in a transport network. High level of powerful graphics offered by most software packages that show individual vehicles traversing networks which include a variety of road categories and junction types [173].

 It has been reported that they are extremely useful tools which could be the next generation of traffic models, and could provide the environmental for discussion for many interested people [181] and [180].

 Nowadays, reasonable low cost and high performance computers enable micro- simulation systems to directly model all the components within traffic systems, [181].

 Furthermore, microscopic simulation models are able to evaluate various traffic management alternatives in order to determine the optimum solution for any traffic scenario and provision of visualization for the case under study [182].

 In reality, traffic data is rarely constant and repeatable, so many reliable suggestions can be offered for different traffic problems such as congestions, incident management etc. which cannot be solved by applying the traditional tools because of their sophisticated transport system [183].

 The models are capable of presenting different evacuation scenarios, the advantage of using simulation – based models is the ability to observe the evacuation plan. Also, they have a wide range of advantages including indication the congestion points and the ability to reduce the computational effort [184].

 And finally, It has been reported that micro-simulation models, such as S-Paramics, are recommended for evaluating various incident management techniques without affecting real road users [132].

4.4.3.1 S-Paramics and its features

S-Paramics (PARAllel MICroscopic Simulation) is good example of the psychophysical models. It is a microscopic vehicle modelling package,‎available‎widely‎and‎the‎UK‟s‎most‎ used to assess the traffic components performance. The S-Paramics is a micro-simulation software‎package‎which‎is‎simply‎defined‎as‎“A powerful communications tool because it is able to present its outputs as a real-time visual display” [177].

Historically, S-Paramics has been introduced to be used in an emergency evacuation area since 2002. Church and Sexton have employed S-Paramics to obtain the clearing time estimates under different evacuation scenarios. Various input data have been adopted such as different combinations of demand level, normal traffic and traffic control [184].

It has been concluded that the S-Paramics is a software system that could simulate the individual components of traffic flow and congestion and presents its output as a real-time visual display for traffic management and road network design [185].

Also, it has been noted that it is one of the new generation of desktop micro-simulation models which has emerged which helps effectively in modelling the evacuation [179]. Thereby, S-Paramics model is characterized as offering the real-time assessment, called dynamic feedback [186] where it shows the driver behaviour within the simulation model.

In other words, S-Paramics represents the actions and interactions of individual vehicles as they travel through a road network and models the detailed physical traffic road. As a consequence, S-Paramics can portray and evaluate the variable circumstances which lead to congestion in all types and sizes of road network [177].

It has been concluded that S-Paramics simulation models provide the ability of modelling individual vehicles in high details, and able to provide various traffic information; such as flow‎ and‎ delay.‎ It‟s‎ used‎ widely‎ in‎ traffic‎ problem‎ such‎ as‎ congestion‎ by‎ simulating‎ the‎ interaction between the road components and the Intelligent Transportation Systems [164]. An ability to interface to other common macroscopic data formats and real-time traffic input data sources [181] . In addition, the Interfaces from S-Paramics to ITS and Urban Traffic Control Systems enable simulation models to be used to develop control strategies for incident and event management and to investigate options for optimizing adaptive signals, and urban or motorway control systems. Figure ‎4.2 below shows an example of this [177].

Figure ‎4.2 Example of S-Paramics [177]

The simulator can model around 200,000 vehicles on around 7,000 roads (taken from real road traffic network data) at faster like 'real-time' rates, large models may extend to hundreds of square kilometres. It is traffic simulation software that is capable of designing and analysing various traffic networks such as complex intersections, merging sections and roundabouts [187] and [177].

Also, S-Paramics is able to model a big city network which requires a large amount of input data. In case of having huge statistical data, S-Paramics is able to simulate in very high speed batch mode operation in addition to its visualized real time environment [181].

SIAS's system, S-Paramics, includes multi models such as car-following lane-changing models, dynamic and intelligent routing.

Various major traffic network data can be analysed and calculated accurately by S-Paramics including the speed, density, flow and delay. So far, no automatic real world system, comprehensive model or even a human could be as precise as demanded. Some of the other advantages of S-Paramics include:

 Easy data entry through a user-friendly interface

 Ability to create evacuation zones

 Ability to create, modify and delete some traffic layouts, such as intersections and roundabouts

 Another important feature of S-Paramics, the component of S-Paramics comprises the main parallel computational element which has the potential to move vehicles around the road network as realistically as possible, taking account of other vehicles, crossing priorities, traffic lights, safe distances and so on [187].