# The Contact Phase in Vehicle-Pedestrian Accident Reconstruction
## 5 Discussion  
The current geometry of cars influences the distances traveled by pedestrians coming into contact with them. In the speed range of 10 m/s to 5 m/s, a large dispersion of the values obtained for the distances traveled by the vehicle in contact with the pedestrian can be observed, both in the case of simulations and in the experimental tests. For low speeds, the possible explanation is the fact that the movement of the pedestrian is not extensive; after the impact in the area of the lower limbs, he/she flips over on the hood and remains in contact until he/she slides in front or on the side of the vehicle. In the simulations that we carried out, the dispersion according to the vehicle class is presented in Table 4. It can be observed that the distance covered during the contact phase between the vehicle and the pedestrians depends on the vehicle class. Thus, SM and CC class vehicles have the longest contact phase distance, followed by CSUV and EC class. The experimental research, amounting to 18 tests, were carried out with different types of vehicles, at various impact speeds, with dummies of different sizes and masses or real accidents, as shown in Figure 29,b. The video images captured during the experiments were analyzed with the aim of establishing the distances traveled by pedestrians in contact with vehicles. They best reproduce the different specific conditions under which accidents involving pedestrians take place. Also, the impact conditions, dry or wet road, varied. An important mention is that the dummies used had various masses and heights, thus covering as large a segment as possible of the anthropometric typologies of people. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Vehicle Class** & **D\({}_{\text{veh}}\)Min** & **D\({}_{\text{veh}}\)Max** & **Ratio Dmax/Dmin** \\ \hline CC & 1.11 & 4.01 & 3.61 \\ \hline CSUV & 0.89 & 2.6 & 2.92 \\ \hline EC & 1.20 & 2.5 & 2.08 \\ \hline SM & 1.13 & 4.2 & 3.71 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Contact distance according to different classes of vehicle. Figure 29: Examples of impact with dummies (**a**,**b**). (**a**) Source [40]. The experimental data confirm the existence of the two sub-phases of the contact between the car and the pedestrian. Superimposing the distances travelled by pedestrians over the simulation results, as displayed in Figure 30, shows a good correlation between them. The large dispersion of the travel distances around the speed of 10 m/s is also evident in the experimental investigations. The comparison between the bilinear model and the theoretical and experimental results changes some aspects of the distance travelled during the contact phase between the cars and the pedestrians. Thus, the reconstruction of traffic accidents can be conducted on the basis of new assumptions. A trendline was identified in order to express the difference between these two models, as seen in Figure 30.  
Future research could develop a new mathematical model of the pedestrian's distance in contact with the car, taking into consideration more factors such as height of pedestrian, different weather conditions dry/wet/icy, different mass and posture of pedestrian during impact. The theoretical simulations were run with four classes of vehicles, with their frontal profile influencing the results obtained. The impact speed directly proportionally influences the distance traveled by the vehicle in contact with the pedestrian and inversely proportionally influences the contact times between them. In the range of speeds 5-10 m/s, the results regarding the distance traveled during the contact phase show the greatest dispersion, both in theoretical simulations and in experimental tests. Low vehicles, such as coupes, hatchbacks or sedans, at high speeds tend to throw the pedestrian on top of them, while SUVs tend to run over the pedestrian at low speeds, having a fairly high ground clearance; therefore, the contact varies depending on the shape of the vehicle.