Present serviceability index

The overall structural adequacy of pavements is given in probabilistic terms of the present serviceability index developed from the AASHTO road test (17). This index, which is a measure of the momentary ability of a pavement to serve traffic, is based on such factors as rut depth, slope variance, cracking, and patching of the pavement. The relationship between serviceability index and these pavement distress modes is given by the AASHTO road test equation (16) ... 

In contrast to all other design methodologies for flexible pavements, the AASHTO methodology uses a pavement performance criterion, which, apart from cracking and subgrade deformation, includes other parameters affecting the performance of the pavement. This criterion is called serviceability, expressed as present serviceability index (PSI). 

Present serviceability ratio and present serviceability index concept... 

The subjectivity of rating the pavement condition by users in terms of PSR has led to the development of the present serviceability index (PSI). The same sections of the AASHTO study were also surveyed at the same time and physical measurements (slope variance in wheel paths, cracking, area of patching and rut depth) were carried out (AASHTO 1962). The PSR estimated from objective physical measurements was termed PSI. The equations derived to determine PSR in an objective way in terms of PSI were as follows ... 

SN = structural number APSI = change in present serviceability index and Mr = resilient modulus of subgrade or base being considered (psi). 

Figure 10. Comparison of present service ability index for sulfur-asphalt and asphaltic concrete...

Al-Omari B.H. and M. Darter. 1994. Relationships between International Roughness Index and present serviceability rating. Transportation Research Record, No. 1435, pp. 130-136. Washington, DC TRB, National Research Council. 

Pyrethroids. Unpublished report of Compliance Services International, Rochester and http //ec. europa.eu/sanco pesticides/public/index.cfm. Values presented are lowest reported no observed effect concentrations in pg/L. 

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