## 3 Results  
Figures 3-8 represent maximum allowable inlet spacings for different roadway widths in each subplot: one-, two-, three-, and four-lanes, based on various road designs and environmental factors. In the figures below, the range of longitudinal and cross slopes, \(S_{L}\) and \(S_{x}\), are shown in the dual X-axes placed below and above the plot area, respectively. Note that \(S_{x}\) values at the top axis does not constitute an increasing reference line, but rather it shows fixed intervals with slopes up to 6%. Each \(S_{x}\) value was combined with \(S_{L}\) values up to 10%, and their outputs for various intensities forms each section within the subplots. The analyses were conducted for four different lane numbers, from one lane up to four, which is the reason for the four subplots within each of the Figures 3-8. The change in colors in the figures shows the change in rainfall intensity \(I\). The lines that cut short or disappear altogether despite showing in the legend attest to the topping of the 4 mm maximum depth criterion for the over-lane flow (except in Figure 8, in which it is for 2 mm). Recall that only the configurations that are free from hydroplaning were considered and the others dismissed because they are unsafe for vehicles. Note that in Figures 3-8, once the trend was clear, in order to make certain profiles more visible, a limit was placed on the maximum allowable inlet spacings: in the one-lane case in Figure 3, for example, the plot is cut beyond 6000 m along the Y-axis. \begin{table}
\begin{tabular}{c c} \hline \hline
**Property** & **Tested Conditions** \\ \hline Roadway roughness, channel flow, \(n\) & 0.016 \\ \hline Roadway roughness, sheet flow, \(n\) & 0.011 (Equation (1)) \\ Runoff coefficient, \(C\) & 0.95 \\ Lane width (m) & 3.6 \\ Shoulder width (m) & 3 (highway) 10 (local) \\ \(T_{\text{max}}\) & Shoulder width (highway) 112 lane width (local) \\ Maximum channel flow depth & 10 cm (alternatively 3 cm) \\ Hydroplaning limit & 4 mm (alternatively 2 mm) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Assumptions considered. \begin{table}
\begin{tabular}{c c} \hline \hline
**Property** & **Tested Conditions** \\ \hline Rainfall intensity (mm/h) & 25–300 \\ \hline Number of lanes on the road & 1, 2, 3, 4 \\ Cross slope (\%) & 1, 2, 3, 4, 5, 6, (and 7) \\ Along-road slope (\%) & 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Conditions used for calculating inlet spacing. For a single-lane pavement, as high as 293 mm h-1 intensity works for all configurations tested, in terms of maintaining the over-lane flow depth within safety limits. When the lane number doubles, the intensity halves; when it triples, the intensity falls to a third (Figure 7). This is consistent for a 3 m shoulder, and Table 6 shows the corresponding over-lane flow depths for four-lane pavement with the rainfall intensities from the figures, based on the analyses in this study. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Rainfall Intensity, \(I\)**} & \multicolumn{10}{c}{**Longitudinal Slope, \(S_{L}\) (\%)**} \\ \cline{2-11}  & **(mm/h)** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** \\ \hline
25 & 1.2 & 1.3 &  
With zero offset and a maximum spread of half the lane from the curb (as in local roads), the spacing limits are pushed farther with the increasing on-grade and cross slopes (Figure 3). Under the given conditions, spacing of kilometers seems applicable for various configurations. For large intensities and lower slopes, however, the hydroplaning limit begins and starts to eliminate certain configurations. Figure 4 captures the orientations that result in shorter inlet spacings in a more visible manner. The cross-slope values range from 2 to 7 percent, as shown in Figure 4, revealing the increase in maximum spacing values with increase in cross slope slows at 6% and starts to drop at 7%, indicating that the turning point is between 5 and 6%.