Study of Pavement Condition Index (PCI) relationship with International Roughness Index (IRI) on Flexible Pavement

Road is an infrastructure that built to support the movement of the vehicle from one place to another for different purposes. Today, it is often found damage to road infrastructure, both local roads, and arterial roads. Therefore, to keep the pavement condition to remain reliable, in Indonesia has a periodic program by conducting an objective functional inspection of roads regulated by Bina Marga using the International Roughness Index (IRI). However, the IRI examination is not sufficient to represent the actual field condition; it is necessary to perform subjective functional examination by appraising the road one of them is Pavement Condition Index (PCI, ASTM D 6433). This method has been widely applied in some countries because it has many advantages. However, to do this inspection requires considerable cost, then there needs to be a model to get the relationship between these two parameters of the road. The selected case study was arterial road segment in Medan City, that is in Medan inner ring road. Based on the results of the analysis, there is a difference between the functional conditions of PCI and IRI. The equation derived from these two parameters is by exponential regression equation, with equation IRI = 16.07exp . with R of 59% with correlation coefficient value (r) of -0.768. The value of R indicates that PCI gives a strong influence on IRI value.


Preliminary
Nowadays, it is often found damage to road infrastructure, both local roads, and arterial roads. The condition, of course, will also disturb the convenience and endanger the road users. Technically, road damage indicates a situation where the structural and functional roads are not able to provide optimum service to the traffic crossing the road. In general, the functional performance of the path can be determined by 2 (two) ways, i.e., objectively and subjectively. Objectively, pavement performance is obtained from a measurement using roughness measuring instrument, whereas in a subjective way it is based on the observation of several experts directly in the field (Suwardo, 2004). One parameter of pavement performance that can be objectively determined is roughness and can be subjectively determined by assigning a value to Pavement Condition.
In Indonesia, the road functional appraisal method is issued by DGH. This method assesses pavement level conditions by combining the value of International Roughness Index with Surface Distress Index (SDI). However, some studies show that SDI tends not to represent the real state of affairs, so a survey method that is more likely to describe the actual functional conditions of the road, one of them is Pavement Condition Index (PCI). However, this PCI functional survey method requires time, cost and labor not a little. With such regular road conditions, it is necessary to create a model illustrating the relationship between IRI and PCI values, thereby improving the results of better identification of the functional conditions of the roads to make appropriate decisions for the road conditions.

Pavement Condition Index (PCI, ASTM D 6433)
Pavement Condition Index (PCI) is a method of assessing pavement conditions developed by U.S Army Corps of Engineer, expressed in the Pavement Condition Index (PCI) index. The use of PCI for the evaluation of airport pavements, roads and parking lots has been widely used in the United States. In the PCI method, the degree of pavement damage is a function of 3 main factors, namely:

Distress severity
The severity of pavement damage on the PCI method, divided into 3 (three) levels, namely low (1), medium (m) and high (h). Determination of the severity for the type of damage has been defined by the PCI method clearly in accordance with ASTM D 6433.3.

Distress quantity
Distress quantity relates to measurement, measurement unit and total quantities on survey form.

International Roughness Index (IRI)
International Roughness Index (IRI) is a parameter used by the world bank for in the process of assessing the condition of pavement in 1980. Unevenness is a prolonged profile picture of the pavement which is a picture of the comfort of driving on the highway. This quantitative value of unevenness is expressed in the International Roughness Index (IRI), i.e., the cumulative length of rising and fall of the surface per unit length in which IRI units are shown in meters down the length of road miles (m / km).

Data collection and analysis
Data collection was done in the field, i.e., functional road examination by PCI and IRI method divided into 50 meters. PCI survey with reference ASTM D6433, while for the review of roughness (IRI) using Roughometer III tool obtained from BBPJN II Medan. The analysis of the relationship between the two parameters is done by using SPSS commercial software, which is done by making the regression equation in some equation. That gives the value of R 2 used as the result of the equation of the two relations.

Roughometer III
Roughometer III is a device that measures the ruggedness by eliminating the effect of the used vehicle components, such as suspension or passenger load, i.e., by directly measuring the shaft movement with the Accelerometer precision.
Noteworthy in the installation of this tool is that all components must be installed in place, and calibration before use must be tailored to the needs.

Analysis of road condition assessment with PCI
The steps to get the PCI value are as follows:

Analysis of road condition assessment with IRI
IRI examination results are done by connecting controller Roughometer III with computer, then obtained the results of the examination. However, to determine the overall functionality that the PCI survey has undertaken, the location of this study is categorized as a Good road segment, where the IRI value is between 2 -4 m / km. There are several types of relationship model between IRI and PCI, all of which will give a coefficient of determination value (R 2 ), in this research, the most significant value of R 2 with exponential equation. − .

Analysis of PCI relationship with IRI
has value of R 2 is 59% and correlation coefficient value (r) is -0.768.

Poor
Fair 44.3% R 2 tends to decrease due to road damage which because of this road has a road characteristic of its own. For Gagak Hitam street, which has four lanes and two directions, it is dominated by light vehicles. As for the 1.5 km Asrama street, it is dominated by heavy vehicles entering from Binjai City, so it has different traffic loads with Gagak Hitam street. In contrast to Kapten Sumarsono's street, there is a narrowing of the road which is laid to the previous road four lanes, narrowing into 2 lanes 2 directions without a median. This implies that the traffic load tends to increase.

Following the division of the Rating Scale Pavement
Condition Index, the road segment in the study location is classified as fair, with an average PCI value of 58.6. The dominant types of damage are rutting, alligator cracking, patching & cut utility, and lane/shoulder off. Meanwhile, based on the IRI assessment, the road segment is classified as a good quality road, with an IRI score ranging from 2 to 4. 2. In addition to differences in the scoring scale, the IRI values obtained tend to be less close to the field conditions. This is because the value of IRI is obtained from the amount of rise and fall of the roughness sensor mounted on the axle of the survey vehicle so as to cause the sensor to read only the surface of the road through the wheels of the vehicle. 3. Based on the value of the coefficient of determination, the relationship between PCI and IRI is quite strong. The value of R2 of 0.59 indicates that 59.0% of PCI value has an IRI value, and R-value is -0.768, which means that the correlation level of these two parameters is strong but opposite.

Recommendation
Concerning the results of this study, some suggestions may be given as follows: 1. Following the division of the Rating Scale Pavement Condition Index, the road segment in the study location is classified as fair, with an average PCI value of 58.6. The dominant types of damage are rutting, alligator cracking, patching & cut utility, and lane/shoulder off. Meanwhile, based on the IRI assessment, the road segment is classified as a good quality road, with an IRI score ranging from 2 to 4. 2. In addition to differences in the scoring scale, the IRI values obtained tend to be less close to the field conditions. It is because the value of IRI is derived from the amount of rising and fall of the roughness sensor mounted on the axle of the survey vehicle to cause the sensor to read only the surface of the road through the wheels of the car. 3. Based on the value of the coefficient of determination, the relationship between PCI and IRI is quite strong. The value of R 2 of 0.59 indicates that 59.0% of PCI value has an IRI value, and R-value is -0.768, which means that the correlation level of these two parameters is strong but opposite.