# An Analysis of Vulnerable Road Users Overtaking Maneuver along the Urban Road
## 3 Results
### Effects of Different Factors on Driver Behavior
#### 3.3.2 Initial Speed of Vehicle  
Each driver had 48 samples in total and 12 samples/types of the initial speed. So that, there were 24, 84, 72, 36 samples/types of initial speed for type A, type B, type C, and type D, respectively.  
The Repeated Measures ANOVA tests on LPG did not reveal a significant effect of vehicle's initial speed for all drivers' types, F(3, 39) = 0.161, \(p\) > 0.05 (type A); F(3,177) = 1.105, \(p\) > 0.05 (type B); F(3,141) = 1.88, \(p\) > 0.05 (type C); F(3,105) = 1.03, \(p\) > 0.05 (type D), respectively.  
The analysis of the influence of initial speed on LPG showed new information compared to previous research [2,20]: although each group had its own LPG range, there was no statistically significant effect of different initial speeds in each group behavior. This non-significant result in driver's LPG's perception across speed conditions is instructive for two reasons. First, it shows that the vehicle's initial speed did not have any effect on the experimenter's perception of the lateral gap. Second, it suggests that the results of this study can be compared to other studies which researched on overtaking behavior on a straight road with different speed.  
On the contrary, the Repeated Measures ANOVA tests on RMS showed a statistically effect of initial speed for all type A, type B, type C and type D of drivers: F(1.03,40.34) = 13.45, GGe = 0.825, \(p\) < 0.0001, \(\eta^{2}_{\text{G}}\) = 0.495; F(2.46,145.02) = 52.82, GGe = 0.785, \(p\) < 0.001, \(\eta^{2}_{\text{G}}\) = 0.266; F(2.07,97.06) = 58.68, GGe = 0.688, \(p\) < 0.001, \(\eta^{2}_{\text{G}}\) = 0.451; F(1.93,67.5) = 5.19, GGe = 0.643, \(p\) < 0.01, \(\eta^{2}_{\text{G}}\) = 0.087, respectively. In those tests, [PERSON]'s Test of Sphericity indicated that the assumption of sphericity had been violated, and therefore, a Greenhouse-Geisser correction was used. TukeyHSD tests disclosed statistically significant different between most pairs of initial speed for all types of drivers (Table 5).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Type A** & **Type B** & **Type C** & **Type D** \\ \hline LPG & **\(\ast\ast\ast\ast\ast\ast\ast\ast\ast\ast\) & - & \(\ast\ast\ast\ast\ast\ast\ast\ast\ast\ast\) \\ \hline \hline \end{tabular}  
Significance sign: (-) \(p\) > 0.05 (\(\ast\)); \(p\) < 0.05 (\(\ast\)); \(p\) < 0.01 (\(\ast\ast\ast\ast\ast\ast\)); \(p\) < 0.001; (\(\ast\ast\ast\ast\ast\ast\ast\)) \(p\) < 0.0001.  
\end{table}
Table 4: TukeyHSD tests’ result for lane width effect.  
For all types, the initial speed had a statistically significant effect on how the drivers regulated their vehicle speed. This finding can be explained as the perception of collision to VRU is different across velocities: the higher the speed, the smaller the time-to-collision for drivers to consider the situation and decide to take a maneuver. Moreover, for type A drivers, there was no difference in overtaking strategies between the initial speed of 30-40 km/h. Type D drivers' strategy was different only in the case of an initial speed of 60 km/h.