# Analysis of the Severity of Heavy Truck Traffic Accidents Under Different Road Conditions
## 5 Mechanism Analysis of Heavy Truck Traffic Accident Severity
### Mechanism Analysis of Expressway Accidents
When the road alignment is curved or sloped, the probability of fatal accidents is 5.228 times that of straight sections. First, curved and sloped road sections can affect the driver's visibility. Second, heavy trucks have notable characteristics such as a high center of gravity and heavy loads, and they travel at high speeds on highways. This makes them prone to overturning when navigating curves and susceptible to brake failure during long descents, which can lead to severe traffic accidents. 4. Environmental aspects: Visibility is a significant factor affecting heavy truck traffic accident severity on expressways. As visibility increases, the probability of fatal accidents first increases and then decreases. When visibility is below 50 m, the probability of fatal accidents is the lowest. At 100-200 m visibility, the probability of fatal accidents is the highest, being 3.292 times that of visibility below 50 m. The probability of severe traffic accidents is lowest when visibility is below 50 m because, under such conditions, traffic management authorities implement strict control measures, such as speed limits of 20 km/h, traffic restrictions, diversion, guidance, and even highway closures. In contrast, visibility between 100 and 200 m typically corresponds to less stringent traffic control measures, and some drivers may ignore these controls, driving as if visibility were greater than 200 m. This compromised visibility and field of view for heavy truck drivers can lead to severe traffic accidents, such as rear-end collisions. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Influencing Factors** & \(\beta\) & **Standard Error** & **Wald** & **df** & **Significance** & **Exp (\(\beta\))** \\ \hline
**Accident Types** & & & 16.011 & 3 & 0.001 & \\
1 = Side Collision & \(-1.522\) & 0.643 & 5.607 & 1 & 0.018 & 0.218 \\
2 = Rear-end Collision & \(-0.454\) & 0.576 & 0.620 & 1 & 0.431 & 0.635 \\
3 = Other Collision & \(-1.387\) & 0.595 & 5.430 & 1 & 0.020 & 0.250 \\
**Violations** & & & & 23.266 & 13 & 0.039 & \\
1 = Not Following Lane Regulations & \(-1.120\) & 0.827 & 1.834 & 1 & 0.176 & 0.326 \\
2 = Not Maintaining Safe Distance in Same Lane & \(-0.660\) & 0.689 & 0.916 & 1 & 0.338 & 0.517 \\
3 = Illegal Parking & 0.265 & 0.743 & 0.127 & 1 & 0.722 & 1.303 \\
4 = Not Yielding as Required & 0.279 & 1.077 & 0.067 & 1 & 0.795 & 1.322 \\
5 = Vehicle Not Meeting Technical Standards & 0.709 & 0.761 & 0.867 & 1 & 0.352 & 2.032 \\
6 = Violating Traffic Signals & 0.749 & 1.001 & 0.561 & 1 & 0.454 & 2.116 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Regression Analysis Results of Heavy Truck Accidents on Expressways. The analysis of the mechanism of heavy truck traffic accident severity on expressways reveals that speeding, violating traffic signals (traffic signs, traffic markings), vehicles not meeting technical standards, curved or sloped road alignment, car-pedestrian accidents, and visibility at 100-200 m are risk factors leading to fatal accidents on expressways.