# Analysis of the Severity of Heavy Truck Traffic Accidents Under Different Road Conditions
## 2 Data Preparation
\begin{table}
\begin{tabular}{l c c c} \hline \hline  & \multicolumn{4}{c}{**Variable Frequency**} \\ \cline{2-4}  & \multicolumn{1}{c}{**Urban Roads**} & \multicolumn{1}{c}{**Highways**} & \multicolumn{1}{c}{**Expressways**} \\ \hline
**Age** & & & \\ Under 30 & 55 & 71 & 58 \\ \(>\)30–40 & 206 & 238 & 220 \\ \(>\)40–50 & 184 & 199 & 202 \\ Above 50 & 65 & 45 & 49 \\ \hline
**Driving experience** & & & \\ Under 5 years & 43 & 32 & 32 \\ \(>\)5–10 years & 128 & 123 & 110 \\ \(>\)10-15 years & 132 & 164 & 151 \\ \(>\)15–20 years & 109 & 112 & 108 \\ Above 20 years & 98 & 122 & 128 \\ \hline
**Driving status** & & & \\ Straight & 249 & 393 & 426 \\ Non-straight & 261 & 160 & 103 \\ \hline
**Accident types** & & & \\ Side Collision & 275 & 205 & 44 \\ Rear-end Collision & 15 & 103 & 384 \\ Other direction Collision & 69 & 77 & 62 \\ Non-vehicle Accident & 151 & 168 & 39 \\ \hline
**Accident forms** & & & \\ Collision moving Vehicle & 377 & 415 & 356 \\ Collision stationary Vehicle & 53 & 63 & 131 \\ Single Vehicle Accident & 4 & 14 & 17 \\ Scrape or Run Over Pedestrian & 50 & 44 & 22 \\ Other Inter-vehicle Accident & 26 & 17 & 3 \\ \hline
**Road surface conditions** & & & \\ Wet & 45 & 32 & 40 \\ Dry & 465 & 521 & 489 \\ \hline
**Intersection section types** & & & \\ Intersection * & 286 & 259 & 39 \\ Section & 224 & 294 & 490 \\ \hline
**Physical isolation conditions** & & & \\ Center Isolation & 276 & 105 & 100\% \\ Vehicle-pedestrian Isolation & 21 & 24 & \\ Center + Vehicle-pedestrian Isolation & 27 & 17 & \\ No Isolation & 186 & 407 & \\ \hline
**Roadside protection measures** & & & \\ Protection & 330 & 146 & 474 \\ No Protection & 180 & 407 & 55 \\ \hline
**Road safety attributes** & & & \\ Hazard & 105 & 205 & 160 \\ No Hazard & 405 & 348 & 369 \\ \hline
**Road alignment** & & & \\ Curved or Sloped & 15 & 29 & 33 \\ Straight and Level & 495 & 524 & 496 \\ \hline
**Weather** & & & \\ Overcast & 45 & 31 & 43 \\ Rain/Snow/Fog & 24 & 25 & 31 \\ Sunny & 441 & 497 & 455 \\ \hline
**Visibility** & & & \\ Under 50 m & 21 & 90 & 62 \\ \(>\)50–100 m & 109 & 140 & 173 \\ \(>\)100–200 m & 108 & 101 & 117 \\ Above 200 m & 272 & 222 & 177 \\ \hline
**Lighting conditions** & & & \\ Daytime & 260 & 258 & 117 \\ Night with Streetlights & 222 & 163 & 174 \\ Night without Streetlights & 28 & 132 & 238 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Descriptive statistics and assignment of independent variables. Statistical analysis of heavy truck accidents across the three road types in Table 2 reveals similarities in driver characteristics. Driver age primarily falls between 30 and 50 years, with the 30-40 age group comprising the largest share at 40.4%, 43.4%, and 41.6% across the road types. In terms of driving experience, most drivers have between 5 to 20 years of experience, with those having 10-15 years of experience making up the highest proportion at 25.9%, 29.7%, and 28.5%. Regarding vehicle status, there are distinct features of heavy truck accidents across the different road types. On highways and expressways, accidents mainly occur when vehicles are driving straight, whereas in urban areas, straight and non-straight driving accidents are roughly equal. Side collisions are more frequent on urban roads and highways, while rear-end collisions dominate on expressways. Additionally, accidents involving stationary vehicles are significantly higher on expressways compared to urban roads and highways. Regarding road conditions, there are significant differences in the intersection section types, physical isolation conditions, and roadside protection measures at the locations where heavy truck traffic accidents occur across the three types of roads. On urban roads and highways, accidents occur almost equally at intersections and on road sections. However, on expressways, accidents predominantly occur on road sections, with only a few occurring in merging and diverging areas.