Since the road management paradigm has changed into the user-oriented circumstance, the functionality of the crucial road maintenance factors became important than before. Among these factors, the roughness directly related to the ride quality for driver became to get more attention. IRI(International Roughness Index) is recently the most widely used roughness indices in the world. IRI is a reasonable index that reflects the vertical displacement(bounce) of vehicle as the road profile changes. Since IRI reflects the vertical behavior of vehicle, it reflects ride quality indirectly. However, there are various rotational behaviors such as roll, yaw, and pitch in addition to the vertical displacement. Profiles, which MRI range was 1.13-4.12m/km, were measured in five sections and the profiles were entered into CarSIM to simulate vehicle behavior. As a result, the pitch was the largest in all sections, followed by roll and yaw, relatively. Especially, the amount of yaw is about 5% of the pitch or about 7% of the roll. The behavior of moving vehicle was measured using INS(inertial navigation system) and accelerometer in the section where the road surface profile was measured. As a result, as in the simulation, the pitch was the largest in all the sections and the amount of yaw is only about 7% of the pitch or about 18% of the roll. Field experiments were conducted to analyze the effect of the rotational behavior of the actual driving vehicle on the ride quality. 33 panels evaluated the ride quality on a ten-point scale while driving on 35 sections with various roughnesses. 35 test sections were selected considering the roughness distribution of actual expressway. The panel was selected considering age, driving experience, gender, and expertise. Of the total 1,155 responses, 964 responses were used for the analysis, except 191 responses measured at low driving speeds. In addition, the amount of vehicle behavior and road surface profile were measured using INS and laser. As a result of correlation analysis between MPR(mean panel rating) and vehicle behavior, correlation coefficient of bounce was the highest with 0.814, and the order of pitch was 0.798, and roll was 0.734, relatively. As a result of regression analysis for predicting ride quality, regression model combining bounce and roll was statistically the most suitable. This model is expected to reflect the ride quality more effectively because it can consider the vehicle behavior due to the longitudinal profile change of the road surface as well as the vehicle behavior due to the difference between the left and right wheel path road profile.

In general, the road roughness is managed by the roughness factor(or level, index) which is numerically or quantitatively generated(or converted) from the surface profile. However, it should be mentioned that the various roughness indexes including IRI(i.e. International Roughness Index) consider only vertical displacement and one longitudinal profile. In this research, the new roughness index, which evaluates reasonably the ride quality, was developed through the extensive correlation analysis between various vehicle behavior and ride quality. The bounce and pitch of moving vehicle are caused by the change of longitudinal profile. On the other hand, the roll is caused by the difference of the left and right profiles. Since the pitch is caused by the bounce difference between the front and rear axles of a vehicle, the two values occur in a similar pattern. In this study, the bounce and roll of a vehicle were predicted with a half car model, which is connected with two quarter car models. A half-car model was used to calculate the roll rotation angle of the vehicle body according to the change of the road profile. The roll rotation angle was used to calculate the coordinates of the head position of the passenger in the passenger seat. Finally, the coordinates were used to calculate the horizontal and vertical displacement of the head position. The new roughness index is the cumulative RMS value of the horizontal and vertical displacement occurring at the head position while moving at a speed of 80 km/h per km. The first and second experiment results presented that the coefficient of determination(i.e. R2) for the new roughness index was the highest with 0.80. Moreover, the R2 values of MRI, HRI, and RN were also relatively high such as 0.73 ~ 0.79. The feasibility test was conducted on sections that show the greater IRI variation between left and right wheel-pass among the pilot sites. Because a prediction result came from MRI and IRI, the difference between KERI and MRI was relatively lager with the increment of IRI difference between right and left wheel-pass. In this case, the roll was high, and the satisfaction of the ride quality was relatively low. Based on the other field survey results obtained in Seoul, the portion of IRI difference between left and right wheel-pass was above 0.4m/km that presented approximately seven times higher value than the measured IRI values on the expressway. In addition, the sectors showed IRI difference level higher than 2.0m/km were approximately 70 times higher than those in expressway. Thus, it is possible that the KERI could successfully and reasonably evaluate the ride quality on various road types.

Since 2010, old concrete pavement of expressway in Korea has approached the design life or exceeded it. As a result, the amount of maintenance for various types of distresses has also been increasing. In addition, there is increasing a demand for improvement in riding quality due to poor roughness. In this paper, when applying a diamond grinding method (DG) to improve the functionality of aged concrete pavement, a program to predict the 3D road surface profile was developed. Two field tests were conducted for program verification, and the comparison with the existing program and equipment was performed. As a result of the evaluation, the predicted result of the program was very similar to those actually measured using the existing roughness measuring equipment, and the error of the two results was about 5%. As a result of the roughness prediction using the 2D road surface profile measured before DG construction, it was similar to the existing program ProVAL. Using the data obtained by the 3D profile measuring equipment, it is confirmed that the prediction of how the IRI of the road will change in 3D is possible. In the future, through supplementary algorithms and economic analysis modules, it is possible to provide a tool for efficient budget execution of road maintenance agencies.

As a surface treatment method of concrete pavement in Korea, transverse tinning has initially been applied to improve drainage and friction at first. Since 2003, in order to reduce the noise of concrete pavement, longitudinal tinning have been studied and proved its superiority. Therefore, Korea Expressway Corporation (KEC) has applied this as surface texturing method in concrete pavement from 2008 to the present. However, the lateral vibration during vehicle running has been continuously raised in the longitudinal tinning section, and lots of efforts have been made to solve this problem. Nonetheless, complaints still occur intermittently in some sections. In this research, three sections in which complaints occur and three test sections were chosen to evaluate characteristics of lateral vibration between tire and longitudinal texturing. Based on the literature survey on the correlation between longitudinal texturing and tire, evaluation of the site and FEM analysis of each road surface were carried out. As a result of the analysis, the lateral vibration occurred most frequently in the random tinning section compared to other sections, and it was relatively few at the other improved tinning of the test section. Further studies on various tire types and timing intervals in the future will provide a standard of longitudinal texturing, which will reduce lateral vibration.

Recently, as road users have become increasingly important, the importance of functional performance as much as structural one has been important to provide comfortable and safe road services. As a result of the survey on the customer satisfaction of the highway, the road surface condition is selected as the most important area of the road service, and the functional performance such as driving comfort and noise is pointed out as an important problem. Therefore, many studies have been conducted to improve this problem. In most cases, there is a fundamental limitation in providing a comfortable road to the user through the roughness management of the final layer. In this paper, a study was carried out to improve the roughness of the final layer by controlling the roughness of each layer. In construction field of Busan-ChangWon expressway, roughness was measured by three methods according to construction phases of subbase, 1st and 2nd base layer, intermedia layer and surface layer. As a result of the analysis, it was found that the roughness of the lower layer affects the roughness of the upper layer. Especially, the roughness of 1st base layer was relatively clear correlation with the intermedia and the surface layer IRI. In the future, after getting more field data and establishing the management standards, it is possible to provide a comfortable road to users.