## 1 Introduction  
In most urban areas, there is an on-going increase in the number of vehicles on the road. For road authorities, taking measures to improve traffic efficiency and the safety of its participants is essential. Amongst research in this field [1; 2; 3], studies on traffic theories [3], models [4], and traffic modelling for one- and two-way roads and also roundabouts appear to be the most promising. Such analyses are significantly facilitated by computer simulations [5], which help to visualise the object of the research. A roundabout is an intersection where traffic moves in a circle around a central island. According to roundabout traffic rules, vehicles approaching a roundabout must give way to vehicles already moving in the roundabout. Roundabout intersections help to solve number of the problems encountered by the traditional intersection which involves a major and a minor road. Roundabouts reduce the number of vehicle-vehicle and vehicle-pedestrian collision points at an intersection, which in turns helps reduce the number of accidents. Research studies conducted in the US have shown a drop in the number of accidents (by 29%) and injured persons (by 81%) as a result of implementing roundabouts [6]. An important aspect of roundabouts implementation is making drivers slow down when approaching a roundabout, which results from the need to give way to vehicles already moving around the roundabout, and from the appropriate structure of a roundabout. [PERSON] and [PERSON] [7] found vehicle velocity has a tremendous effect on the scale of injuries sustained by a pedestrian hit by a vehicle: slowing down from 48 km/h to 32 km/h means the pedestrian's chances of surviving increase ninefold. In a study in Sweden [8], major factors of roundabout safety were specified: the number of lanes in a roundabout, island diameter, and also traffic speed and intensity. The authors of the study argued that single-lane roundabouts are the safest, whereas large-radius roundabouts result in a higher permissible speed, which is positively related to the number of accidents. At the same time, a radius of less than 10 m is also problematic as it usually encourages drivers to accommodate the bend, and consequently drive almost straight on without reducing a reduction in speed. Computer simulations are applied in roundabout traffic modelling to visualise the effects of layout changes. Simulations by their nature obtain information on a given system during the design stage. Computer simulation can also apply hypothetical conditions to a given system. They can provide an examination of the system operation in conditions which occur rarely and conditions yet to eventuate, such as the simulation of the effect of new traffic regulations). Simulation programs are based on mathematical models (traffic flows, multi-agent models, neural networks and cellular automata), which map the process and enable specification of input parameters that affect the simulation effectiveness. For example, [PERSON] and [PERSON] have determined, by means of a simulation, that roundabouts are particularly recommended in places where the traffic is evenly spread among the feeder roads, and also in places where there is a substantial amount of left-turn traffic (in the case of right-hand traffic) [9]. The pair [10] established factors that affect the capacity of roundabouts, and found that a three-lane roundabout is not necessarily preferable to a two-lane roundabout. The mentioned examples of studies show that the focus of the research to date has been to ascertain whether a roundabout is preferable to a conventional intersection, and how many lanes in a roundabout is best to ensure optimal traffic flow. The majority of cities face a problem of chronic jammed streets and roundabouts notwithstanding the studies and road traffic regulations established. There have been numerous examples of drivers who fail to obey rules and cause congestion. The human factor is a significant variable any simulation of traffic.