# Speed Reduction Capabilities of Two-Geometry Roundabouts
## 3 Results
### Roundabout Schemes with Fixed (y)  
In the second part of the investigation, the circulatory roadway width along the minor axis (y) was fixed to 5.5 m to meet the requirements of Condition 1 and Condition 2. This resulted in reduced circulatory roadway widths along the major axis (x), as shown in Table 5. It can be noted that the resulting circulatory roadway width along the major axis (x) was proportional to roundabout size, namely, the major and minor axes (a and b). The results of the swept path analyses for the right turn and straight passage were the distances between the tangent of the entry radius and the tangent of the exit radius along the major and minor axes (L and L\({}^{\prime}\)) and the deflection along the major and minor axes (U and U\({}^{\prime}\)), given in Tables 6 and 7. It can be noted that these distances and the deflections are proportional to the length of the major axis (a). Measured distances between the tangent of the entry radius and the tangent of the exit radius along the major and minor axis (L and L\({}^{\prime}\)) did not change after the intervention in circulatory roadway width along the minor axis (y). At the same time, measured deflections along the major axis (U) are all smaller than measured deflections along the major axis (U\({}^{\prime}\)). It can be also noted that these measured deflections are smaller than the deflections on roundabout schemes with variable (y) and that this difference is inversely proportional to the length of the major axis (a). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**a (m)**} & \multicolumn{2}{c}{**b/a = 0.75**} & \multicolumn{2}{c}{**b/a = 0.80**} & \multicolumn{2}{c}{**b/a = 0.85**} & \multicolumn{2}{c}{**b/a = 0.90**} & \multicolumn{2}{c}{**b/a = 1.00**} \\  & **L (m)** & **U (m)** & **L (m)** & **U (m)** & **L (m)** & **U (m)** & **L (m)** & **U (m)** & **L (m)** & **U (m)** \\ \hline
18 & 54.06 & 3.34 & 53.51 & 4.27 & 57.17 & 5.24 & 61.20 & 6.27 & 64.63 & 8.20 \\
19 & 54.52 & 4.02 & 57.26 & 5.07 & 58.47 & 6.04 & 62.76 & 7.16 & 69.66 & 9.30 \\
20 & 56.09 & 4.76 & 59.26 & 5.87 & 62.76 & 6.99 & 64.89 & 8.07 & 71.44 & 10.30 \\
21 & 62.98 & 5.69 & 61.75 & 6.69 & 65.20 & 7.86 & 62.37 & 8.53 & 75.60 & 11.37 \\
22 & 63.13 & 6.36 & 65.32 & 7.54 & 68.83 & 8.76 & 74.11 & 10.05 & 79.15 & 12.42 \\
23 & 64.02 & 7.07 & 68.38 & 8.37 & 70.85 & 9.61 & 74.80 & 10.90 & 83.36 & 13.55 \\
24 & 67.99 & 7.89 & 71.44 & 9.21 & 75.21 & 10.55 & 78.90 & 11.88 & 87.44 & 14.62 \\
25 & 71.66 & 8.70 & 74.33 & 10.05 & 77.27 & 11.40 & 82.53 & 12.88 & 91.66 & 15.79 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Distances between the tangent of the entry radius and the tangent of the exit radius along the major axis (L) and deflections along the major axis (U) for roundabout schemes with fixed (y). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**a (m)**} & \multicolumn{2}{c}{**b/a = 0.75**} & \multicolumn{2}{c}{**b/a = 0.80**} & \multicolumn{2}{c}{**b/a = 0.85**} & \multicolumn{2}{c}{**b/a = 0.90**} & \multicolumn{2}{c}{**b/a = 1.00**} \\  & **x (m)** & **y (m)** & **x (m)** & **y (m)** & **x (m)** & **y (m)** & **x (m)** & **y (m)** & **x = y (m)** \\ \hline
18 & 10.00 & 5.50 & 9.10 & 5.50 & 8.20 & 5.50 & 7.30 & 5.50 & 5.50 \\
19 & 10.25 & 5.50 & 9.30 & 5.50 & 8.35 & 5.50 & 7.40 & 5.50 & 5.50 \\
20 & 10.50 & 5.50 & 9.50 & 5.50 & 8.50 & 5.50 & 7.50 & 5.50 & 5.50 \\
21 & 10.75 & 5.50 & 9.70 & 5. To provide the visualization of the investigation results (given in Tables 6 and 7 and Appendix A, Tables A3 and A4) in as simple a way as possible, 50 simple linear regression models were defined taking the major axis (a) as an independent variable and measured values (L, L\({}^{\prime}\), U, U\({}^{\prime}\), R\({}_{\rm i}\), and R\({}^{\prime}\)\({}_{\rm i}\), where i = 1-3) for different (b/a) relations as dependent variables (Figures 9-13). It should be emphasized here that these simple linear regression models were not intended for use in the two-geometry roundabout's design.