## 4 Overview of RIGHTrack Full-Scale Pavement Test Track  
The RIGHTrack, for which this research based, is the first full-scale pavement test track of road fields in China. It is located in Beijing, where the average air temperature of the coldest month is \(-4.6\)\({}^{\circ}\)C and the average air temperature of the hottest month is 25.8 \({}^{\circ}\)C. The RIGHTrack, with a total length of 2039 m, is an enclosed curve composed of straight lines and circular curves, with a north-south trend and a symmetrical arrangement. The long-term observation data of each pavement structure of the RIGHTrack is selected to carry out the model accuracy analysis, for several reasons. First, various pavement structures paved by the RIGHTrack are very representative in China, basically covering more than 90% of the commonly used pavement structure types on the asphalt pavement of China's expressways. Moreover, each test section of the RIGHTrack was constructed with the same structure thickness, pavement material, and construction technology as the actual project. The width of each test section is 7.5 m, and two inner and outer lanes are set; each lane is 3.75 m wide, the section length is 50-60 m, and the test size is also completely consistent with the actual engineering project. Therefore, these test structures can better reflect the real situation of actual engineering projects, and the performance observations carried out on this basis are also well representative. Second, the evaluation and accuracy analysis of the rutting model requires the support of long-term service performance observation data. We know that the evolution of pavement service performance is a long-term process. If calculated according to natural life, the service life of pavement usually reaches several decades, which is too long for model verification, and it is difficult and impractical to obtain continuous observation data for decades. The RIGHTrack is a very efficient accelerated loading test platform with the ability to simulate long-term performance in short-term tests. It accelerates the service performance of pavement by increasing the test load of the vehicle. According to the axle load conversion equation, it can be known that each time the test load of the existing RIGHTrack acts once, it is equivalent to dozens or hundreds of times the ESAL of 10 t acts. In this way, the simulation of the long-term service performance of pavement can be realized in the short term. These long-term performance observations can be used to verify the model. Structure I is a semi-rigid base pavement with an asphalt layer thickness of 12 cm, and the structure numbers are STR1 and STR2. Structure II is rigid base asphalt pavement, the structure numbers are STR4 and STR5. Structure III is a semi-rigid base pavement with an asphalt layer thickness of 18 cm, and the structure numbers are STR7 and STR8. Structure IV is inverted asphalt pavement, and the structure numbers are STR10 and STR12. Structure V is a semi-rigid base pavement with an asphalt layer thickness of 24-28 cm, and the structure numbers are STR11 and STR13. Structure VI is a semi-rigid base pavement with an asphalt layer thickness of 36 cm, and the structure numbers are STR16 and STR17. Structure VII is full-depth asphalt pavement, and the structure numbers are STR18 and STR19 [36; 37; 38; 39]. The RIGHTrack layout is shown in Figure 1, and the structure is shown in Figure 2. In the base layer shown in Figure 2, CBG25-I and CBG25-II are cement-bonded graded aggregate material, and the 7-day unconfined compressive strengths are 6 MPa and 4.5 MPa, respectively. CS is cement-stabilized soil, and the 7-day unconfined compressive strength is 2 MPa. LCC and CC are lean cement concrete and cement concrete, respectively. GA is graded aggregate. To ensure test efficiency, heavy trucks are used for the accelerated loading on the RIOHTrack. From December 2016 to December 2018, loading mode I is adopted for loading. The loading vehicles include four three-axle trucks (Figure 3).