Pavement RSL is determined for a given pavement type based on forecasted condition (characterized using individual distress and IRI). Recommended terminal threshold distress/IRI values that define end of service life are presented in Table 44 and Table 45 for new asphalt and asphalt overlaid asphalt pavements and new JPCP and bonded and unbonded JPCP overlays, respectively. Information presented was obtained from review of current highway agency practices and published literature on the subject matter.
|HPMS Surface Type Code||Pavement Type||Distress Type and IRI|
|Alligator Cracking, percent lane area||Rutting, in||Transverse Cracking, ft/mi||IRI, in/mi|
|High Type||Others||High Type||Others||High Type||Others||High Type||Others|
|2, 6, & 7||(2) Bituminous|
(6) Asphalt overlay over existing asphalt pavement
(7) Asphalt overlay over existing jointed concrete pavement
|HPMS Surface Type Code||Pavement Type||Applicability of New Pavement Equations|
|Transverse Cracking, percent slabs cracked||Transverse Joint Faulting, in||IRI|
|High Type||Others||High Type||Others||High Type||Others|
|3, 9||(3) JPCP||12||20||0.17||0.3||177||300|
The PHT Tool determines overall RSL in two ways:
Using a weighted average requires assignments of weights to the individual performance measures. Typically, weights are assigned in order to satisfy analysis objectives. Analysis objectives typically fall into the following categories:
For the first case, RSL due to pavement smoothness is assigned a weight of zero, while all the other structural distresses are assigned weights that add up to 100.
For the second case, RSL due to pavement smoothness is assumed as the pavement RSL. The third and most common method assigned a weight to both functional (IRI) and structural (cracking, rutting, faulting) distresses based on the importance the agency attaches to them. An example of weights applied by Iowa DOT to transform flexible pavement distress data into pavement condition ratings (determined using expert opinion) is presented in Table 46.
|Pavement Distress||Weights||Revised Weights for |
PHT Tool Performance
|Alligator "fatigue" cracking*||10||25|
|Longitudinal cracking (non wheelpath)||5|
|Longitudinal "fatigue" cracking (wheelpath)*||10|
*Both are considered wheelpath fatigue cracking in the PHT Tool.
*Adapted after Resler, J. and O. Smadi. HWYNEEDS: A Sensitivity Analysis. Proceedings: Mid-Continent Transportation Symposium, Ames, Iowa, 2000).
The PHT Tool assigns maximum service life based on pavement type. Computed RSL is replaced by maximum pavement service life if RSL is greater than the maximum service life of the given pavement. Typical maximum service life utilized by the PHT Tool is presented in Table 47.
|Pavement Type||Recommended Maximum Service Life, years|
|Thick AC overlaid AC||10|
|Thin AC overlaid AC||6|
|Thick AC overlaid JPCP||10|
|Unbonded JPCP over rigid pavement||25|
|Bond PCC over JPCP||15|