# Impact of Putting on Traffic Safety: A Synthesis of Research Findings
## 3 Results and Discussion
### Traffic Volume  
The available literature on the impact of traffic volume on the influence of rut depth on accident rates is limited and contradictory, making the task of understanding and explaining its impact challenging. Generally, [PERSON] et al. [13] indicated a higher risk of accidents because of rutting AADT higher than 8000. Figure 6 illustrates the relationship between rut depth and accident rates at different AADT levels based on models developed by [PERSON] et al. [19] for night-time and rainy weather conditions. As presented in Figure 6, accident rates increase with higher AADT for the night-time model, while they decrease for the rain model, given the same rut depth values. Additionally, in the night-time model, the impact of rut depth on accident rates is exacerbated as AADT increases, indicated by the steeper slope of the linear fit. Conversely, in the rain model, increased AADT mitigates the impact of rut depth on accident rates.  
\begin{table}
\begin{tabular}{c c c} \hline
**Country** & **Speed (km/h)** & **Findings Summary** \\ \hline \multirow{4}{*}{Sweden} & 0–50 & No significant impact \\  & 50–100 & Decreased accident rates (up to 50\%) when RD \\  & & increased from 0–5 to 21 mm. \\  & 110–120 (AADT \(<\) 10,000) & Increase in crash rate for RD of 17–21 compared to \\  & & other RD values. \\  & & Decreased accident rates (up to 50\%) when RD \\  & 0–80 & increased from 0–5 to 17 mm. \\ Finland & 80–100 & No significant impact \\  & 100–120 & Increase in crash rate for RD of 17–21 compared to \\  & & other RD values. \\  & 0–90 (AADT \(\leq\) 5000 and \\ Norway & AADT \(\geq\) 10,000) & No significant impact \\  & & Decreased accident rates (up to 50\%) when RD \\  & & increased from 0–5 up to 17 mm. No significant impact \\  & & is observed above 17 mm. \\ \hline \end{tabular}
\end{table}
Table 4: Impact of driving speed on rutting to safety [13].  
Essentially, road geometry influences traffic safety. As illustrated by [PERSON] et al. [41], roads with curved geometry are associated with a higher accident risk compared to straight roads. Multiple field observation and simulation studies have investigated the impact of road geometry on the criticality of putting on traffic safety by comparing straight roads and curved roads [10; 14; 29; 33; 51]. Figure 7 illustrates the relationship between rutting and accident rates considering different road geometries, as reported by [PERSON] et al. [10] and [PERSON] [14]. [PERSON] et al. [10] reported no critical impact of rut depth on accident rate for all roads and curved road models. Differently, [PERSON] and [PERSON] [14] showed a significant impact of rutting, with a higher accident risk on curved roads when the rut depth exceeds 7.6 mm.  
Multiple studies have utilized simulation to investigate the impact of road geometry on the severity of rutting on traffic safety, comparing straight and curved roads [29; 33; 51].  
Figure 6: Influence of traffic volume on the impact of rutting on accident risk [19].  
Figure 7: Influence of road geometry on the impact of rutting on accident risk in field observation studies [10; 14].  
[PERSON] et al. [30] demonstrated that rutting exerts a more pronounced effect on curved roads compared to straight ones due to decreased vehicle stability when drivers attempt to change trajectory or speed. Under wet conditions, [PERSON] et al. [51] concluded that higher rut width and depth consistently pose skid-related safety concerns on curved roads.