# Analysis of the Severity of Heavy Truck Traffic Accidents Under Different Road Conditions
## 7 Discussion
Results indicate that on urban roads, key factors include driver age, vehicle status, road safety features, and lighting. On highways, key factors include vehicle driving status, accident types, roadside protection measures, road safety attributes, and visibility. On expressways, the critical factors influencing accident severity are driver violations, road alignment, accident types, and visibility. These findings demonstrate significant differences in the factors affecting heavy truck accident severity across various road types. Although accident types and visibility are common factors on both highways and expressways, their specific mechanisms differ. For example, on highways, side collisions between vehicles have the greatest impact on accident severity, whereas on expressways, vehicle-pedestrian collisions are the most critical. This difference arises because highways often have roadside access points, which increase the likelihood of side collisions, while expressways are more isolated, leading to a higher risk of vehicle-pedestrian accidents. Additionally, on highways, the effect of visibility on accident severity is linear--the severity increases as visibility decreases. On expressways, the relationship is non-linear; the severity is lowest when visibility is below 50 m, and highest at 100-200 m. This is primarily due to the stricter visibility-related traffic control measures in place on expressways compared to highways. The above findings underscore the importance of analyzing different road types separately when proposing accident prevention strategies. In previous studies, scholars also conducted severity analyses of heavy truck traffic accidents based on different road types. [PERSON] et al. [5] conducted a study under urban road conditions, and the results showed that nighttime driving conditions, single-vehicle accidents, vehicle-pedestrian collisions, not following lane regulations, and traffic signal violations significantly influenced the severity of heavy truck traffic accidents. [PERSON] et al. [19] studied heavy truck traffic accidents on highways and found that daytime crashes, lack of access control, higher speed limits, and crashes on rural principal arterials were the most important factors contributing to higher injury severity. [PERSON] et al. [21] conducted a study under expressways, and their analysis showed that weather conditions, lighting conditions, speeding, and bridge/tunnel sections had significant impacts on the severity of heavy truck traffic accidents. We can conclude that the causes of heavy truck traffic accident severity identified in these studies differ significantly from those found in our study. The primary reason for this discrepancy is the different datasets used. [PERSON], [PERSON], and [PERSON]'s studies were based on foreign traffic accident data, whereas this study is based on Chinese traffic accident data. Different countries have significant differences in terms of laws, road design standards, and driver characteristics. Therefore, when formulating traffic management measures, the primary basis should be research findings based on domestic data, with studies based on foreign data serving as a supplementary reference. Furthermore, this study has some limitations. First, this study is based on data from heavy truck traffic accidents in a specific region of China, so the findings may not be fully applicable to all regions of China. In the future, data from different regions can be collected for a more comprehensive study. Additionally, the conclusions drawn from the logistic regression model in this study are more qualitative. In the future, quantitative research on heavy truck traffic accidents can be conducted using machine learning or deep learning methods, which will provide better support for formulating traffic management measures aimed at preventing heavy truck traffic accidents.