# Determining Factors Influencing Operating Speeds on Road Tangents
## 3 Results
### Dual-Carriageway Road Tangents
#### 3.2.2 Right (Driving) Lane  
In order to explore the relationships between the operating vehicle speed and continuous factors in the right (driving) lane of dual-carriageway road tangents, the same approach to that used for the right (driving) lane of dual-carriageway road tangents was employed. Following the Shapiro-Wilk test, the Pearson correlation coefficient was applied for those variables that were found to be normally distributed, while Spearman's rank correlation was utilized for the remaining variables that did not meet the assumption of normality. The results of both the [PERSON] and Spearman's correlations are summarized in Table 6, which highlights the strength and direction of the relationships between the operating vehicle speed and each of the continuous factors.  
Figure 18: Tukey–Kramer test results—terrain type—left (overtaking) lane of dual-carriageway road tangents.  
For the binary categorical factor (only the emergency lane presence), a \(t\)-test was conducted to test for significant differences in the operating speeds between the two categories. The results of the \(t\)-test analysis are shown in Figure 19.  
For multi-level categorical variables, the relationship between the operating speeds and the different levels within each variable was analyzed using an analysis of variance  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Continuous Factors** & \multirow{2}{*}{**Test Used**} & **Pearson Coeffi-** & \multirow{2}{*}{**Significance Level**} \\
**Dual-Carriageway Roads—Right (Driving)** & & **cient/Spearman’s \(\rho\)** & \\ \hline Total tunnel length in last 20 km & Spearman & \(-\)0.2095 & 0.3754 \\ Previous object distance & Pearson & 0.25115 & 0.2855 \\ Following object distance & Pearson & 0.083631 & 0.7259 \\ Longitudinal slope & Pearson & \(-\)0.10003 & 0.6748 \\ Heavy goods vehicles share (left lane) & Spearman & 0.2591 & 0.2700 \\ Heavy goods vehicles share (right lane) & Pearson & 0.25593 & 0.2761 \\ Heavy goods vehicles share (both lanes) & Pearson & 0.430092 & 0.0584 \\ AADT & Spearman & \(-\)0.3170 & 0.1733 \\ ASDT & Spearman & \(-\)0.5525 & 0.0115 * \\ Traffic flow density (left lane) & Spearman & \(-\)0.7901 & \(<\)0.0001 * \\ Traffic flow density (right lane) & Pearson & \(-\)0.70432 & 0.0005 * \\ \hline \hline \end{tabular}
\end{table}
Table 6: Correlation results—[PERSON] and Spearman’s for continuous factors in the right (driving) lane of dual-carriageway road tangents (Values marked with * indicate statistically significant results at the 0.05 level).  
Figure 19: \(t\)-test result for the binary factor (emergency lane presence)—right (driving) lane of dual-carriageway road tangents.  
(ANOVA). This approach allowed for the assessment of significant differences in the operating speeds across multiple categories. The ANOVA results are shown in Figure 20.  
An analysis of variance (ANOVA) was conducted to investigate the influence of several categorical factors on the operating vehicle speed (V85) in the right (driving) lane of dual-carriageway road tangents. The results showed that, for most factors, there was no statistically significant effect on the operating speed. Specifically, the factors speed limit (\(p\) = 0.6072), lane width (\(p\) = 0.5067), and design speed (Vp) (\(p\) = 0.5067) all resulted in \(p\)-values greater than 0.05, indicating that these factors did not significantly influence the vehicle speed in the right lane. Similarly, the factor terrain type (\(p\) = 0.1172) exhibited a borderline significant effect, with an F-ratio of 2.4380, suggesting potential differences in the speed across terrain types, but failing to meet the conventional significance threshold of 0.05. Given that terrain type approached statistical significance, it was decided to conduct a post hoc Tukey-Kramer test to further explore the pairwise differences between the terrain categories. The Tukey-Kramer test results are shown in Figure 21.  
Figure 20: ANOVA results for multi-level categorical factors—right (driving) lane of dual-carriageway road tangents.