# A Review of Long-Term Skid Resistance of Asphalt Pavement
## 4 Decay and Prediction of Long-Term Skid Resistance of
### Asphal Pavement
#### Influencing Factors, Decay Law, and Model of Long-Term Skid Resistance of Asphal Pavement

Table 4: Influencing factors of the L-TSR of AP. In addition, global scholars generally study the AP L-TSR decay law from the macro and micro aspects [106; 135]. From the macro aspect, starting from the influencing factors, researchers use indoor accelerated loading equipment to simulate the effect of tire rubbing on the road surface through measuring the change rule of AP skid resistance performance indicators under the action of the load to analyze the long-term skid resistance decay law of AP and fit the test data to establish the long-term skid resistance decay model of AP. The microscopic aspect focuses more on analyzing the change rule of parameters related to aggregate surface texture under repeated loads to explore the decay law of skid resistance properties [136; 137; 138]. The asymptotic model, Penn State modified model, PIARC model, friction factor model, and empirical model are the main models for the L-TSR decay of AP. Since the Penn State correction model does not consider the macroscopic structural parameters of the pavement at high speeds, and the test speed (10 km/h) differs greatly from the actual driving conditions, the PIARC model is expensive and difficult to realize indoors, and the friction factor model requires experimental data such as the modulus of elasticity of the pavement and the average stresses of the wheel loads of the vehicle [89; 139]. Therefore, most scholars choose the asymptotic model and empirical model on AP skid resistance decay law research, and many studies have found that the model for the skid resistance index decay are presented as firstly rapid and then slow, and it finally tends to stabilize the law; the accuracy of the fit is high. Based on domestic and international research, the classical L-TSR decay law of AP is shown in Figure 7, and the schematic diagram of AP texture change is shown in Figure 8. AP L-TSR decay law, evaluation indexes, and decay models are shown in Table 5. \begin{table}
\begin{tabular}{c c} \hline
**Influencing** & **Influence Mechanism** \\
**Factors** & **At high temperatures, the elasticity of the AP is stronger, able to absorb a certain amount of loading, delaying the abrasion of the specimen; at low temperatures, the tire stiffness is greater, the asphalt film becomes harder and more brittle, the abrasion effect is stronger, and the AP skid resistance decay rate is larger [132; 133; 134] \\ \hline Rain falls & Rainwater will penetrate into the substrate, affecting the internal structure of the AP, increasing the degree of aging of the AP, and accelerating the deterioration of the pavement’s skid resistance [129] \\ \hline Longitudinal slope and slope & Vehicles need to adjust their speed by braking when traveling on longitudinal slopes of the road. When the car is braking, the friction between the tires and the road surface changes from rolling friction to sliding friction, which increases the friction between the tires and the road surface, and the same section of the road for a long time will lead to a decrease in the slip resistance of the road surface \\ \hline \end{tabular}
\end{table} 
Table 4: _Cont._It can be seen from Figure 7 that the decay of the skid resistance of AP is divided in two different ways; the first is that the initial decline is faster, the middle is slower, and finally tends to be stable; the second is a \"hump-shaped\", with first a brief rise then a rapid decline and finally, a stabilization [143; 144]. The former is because the asphalt film continues to fall off under the wear of the vehicle in the early stage of the AP, and due to the compaction of the tire, the fine aggregate and the asphalt mortar flow to the pavement surface and part of the pavement texture is filled [145]. The cutting effect and extrusion deformation of the road surface on the tire are reduced, resulting in a rapid decline in the skid resistance of the pavement. As the asphalt film continues to fall off, the asphalt-wrapped aggregate is exposed to provide a richer texture.