## 4 Results of the Experimental Studies
### Examining the Impact of the Proposed Changes on the Roundabout Capacity  
Table 4 presents the results of the experiment aimed at examining the impact of different forms of roundabout traffic reorganisation on the roundabout capacity. The mean and median values for the number of iterations have been rounded to integral numbers. The values are similar with each other, which meant that the results were absent outliers. In order to make sure that the analysed results are not distorted, their distribution was visualised in the box plot presented in Figure 8. It shows that the results are scattered in a similar manner, proven by the similar sizes of the boxes and their \"whiskers\". The distribution of the variable is symmetric, \begin{table}
\begin{tabular}{c c c} \hline
**Examined Traffic Scenarios** & **Mean Number of Iterations** & **Median of Iteration Quantity** \\ \hline Scenario 1 & 526 & 524 \\ Scenario 2 & 494 & 493 \\ Scenario 3 & 503 & 502 \\ Scenario 4 & 456 & 456 \\ Scenario 5 & 483 & 482 \\ \hline \end{tabular}
\end{table} 
Table 4: Mean number of iterations and median of the iteration quantity. as the horizontal line in the box representing the median is located more or less in the middle. During the testing of the individual scenarios there were some outliers that are marked with circles, however, their quantity compared to the number of cycles accounts for less than 1% of the obtained results. The chart shows that there is a correlation between the examined scenarios and the quantity of CA iterations. The traffic organisation described in Scenario 4 caused vehicles to cross the roundabout in the shortest time. The worst case of the traffic organisation is represented by the reference scenario, i.e., Scenario 1 (526 iterations on the average). That means an improvement of 15%. The roundabout capacity was calculated (Figure 9) based on each of the obtained results. The guiding principle was the higher the value of the capacity, the better the solution. The measure of roundabout capacity is the quantity of vehicles which exit the roundabout in a time unit which is one iteration of a cellular automaton. The best result was obtained in the case of Scenario 4. The second best result was the roundabout traffic organisation according to Scenario 5. Figure 8: Impact of roundabout traffic organisation on the quantity of cellular automaton (CA) iterations. Figure 9: Impact of traffic organisation on the roundabout capacity. Table 5 shows the percentage differences in relation to Scenario 1. The traffic organisation described in Scenario 4 led to the greatest increase in the roundabout capacity in relation to the current traffic rules (Scenario 1). Scenario 4 is a combination of the rules specified in Scenarios 2 and 3. The changes introduced separately provide an increase of 6.4% and 4.5%, respectively, and cumulatively 10.9%. However, introducing them together increases the roundabout capacity by an extra 4.4%, thus achieving the best result of all the modifications, equalling 15.3%. Such traffic organisation tidies up the road traffic and can be achieved without substantial modifications of the traffic regulations (what it does require is provision of more accurate driver training and at the same time developing appropriate algorithms for autonomous vehicles). The second biggest increment in relation to the reference scenario is demonstrated by Scenario 5. It is an attempt to turn attention to the fact that the traffic regulations in force favour drivers moving along the outer lane of a roundabout. Such vehicles often block roundabouts, while the inner lanes are empty or almost empty. According to the simulations, introducing the changed right of way in roundabouts can cause a result of increase 8.9%, preferable to the status quo (Scenario 1), while at the same time being the second most efficient set of rules. The subsequent studies pertained to the impact of the number of pedestrians at the roundabout on the roundabout capacity for the individual traffic scenarios.