Abstract
<p>The paper presents a joint analysis of some pavement performance indicators based on a system of seemingly unrelated regression equations (SURE) which allows to handle correlated error terms. In particular, three major indicators such as the side friction coefficient (SFC20°C), mean-profile depth (MPD), and international roughness index (IRI), were measured in a case study and subsequently used in analysis. Regression parameters were estimated by the Maximum Likelihood Method and the t-statistic was considered to show the statistical significance of regression coefficients. The results show that estimation points have the signs expected: the SFC<sub>20°C</sub> decreases as the number of accumulated trucks (<em>N</em><sub>t</sub>) increases; whereas the MPD and IRI increase as the number of trucks increases. A likelihood ratio test was also carried out to determine whether the system model, which assumes correlation among error terms, was more appropriate than separate models. In this particular case, with three degrees of freedom, was found that the result corresponds to a p-value 0.150 and the null hypothesis cannot be rejected at any significance level less than this value.</p>
Highlights
Physical measures of road conditions are often used as a basis for determining safety needs, rehabilitation requirements and resource allocation
Three performance indicators of pavement known as the side force coefficient (SFC), the international roughness index (IRI), and the mean profile depth (MPD) were more especially measured in three different time periods on a same section of this motorway
Estimation points have the sign expected for all these models: the SFC20°C decreases as the number of accumulated trucks (Nt) increases; whereas the MPD and IRI increase as the number of trucks increases
Summary
Physical measures of road conditions are often used as a basis for determining safety needs, rehabilitation requirements and resource allocation. The SFC is used to describe the friction between the vehicle tyre and pavement. It is defined as the ratio between the tangential force divided by the normal force at a standard speed. This parameter is expressed numerically by positive values smaller than 1 (or smaller than 100 in some official reports where its value has been multiplied by 100). The SFC is generally thought to be above all associated to road safety
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