The main elements of PERS^® are:

• Material dependent Models for predicting the pavement performance based on mechanistic (analytical) principles.
   
• Models for quantifying the economic effects of pavement conditions.
   
• Empirical Models, which can be calibrated automatically, and used as an alternative to the mechanistic models.
   
• Cost/benefit analysis, for optimizing the maintenance strategy for a section.
   
• Methods for selecting the optimal combination of maintenance and rehabilitation alternatives over a user defined number of budget years (optimisation).

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PERS^® makes use of an incremental-recursive approach for calculating pavement performance.
For each increment of time (normally one season) the damage, caused by traffic loading and time related effects, is calculated.
The new pavement condition is then used recursively as input for the next time increment.

With the Performance and Cost/benefit analysis functionalities PERS^® can evaluate specific maintenance solutions or alternatives PERS^® can automatically, from the list of alternatives, generate a number of possible maintenance plans based on optimizing agency costs or total costs over the lifetime of the pavement.

All included materials and maintenance alternatives, with all their properties and models, can be defined by the user.
These inputs are saved in a Parameter setup table.
It is possible to have multiple setup's to be used with different parts of the road network.

Future traffic volumes can be calculated using global or individual growth factors, or they can be entered manually for section specific information.

PERS^® makes use of historical data.

The simulation of pavement deterioration is started at the first point in time where information is available on the pavement structure (material types, layer thicknesses and moduli).

Any available data on structural condition, roughness, rutting, friction, visual rating or required repair that dates after the start of the simulation, will be plotted together with the deterioration predicted by the performance models.
This allows the performance models to be validated (and adjusted, if need be) and serves as a quality check on the measured performance data.

Several effects of pavement conditions may be quantified.

For multiple types of vehicles the Vehicle Operating Costs (VOC) may be defined as a function of roughness and friction.

The accident costs may be calculated as a function of friction and roughness and an "aesthetic" value may be assigned to the visual rating and included as a user cost.

PERS^® also calculates the agency costs and the changes in capital value caused by deterioration or improvements.

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The following types of damage are considered:

• Structural deterioration in the form of decrease in the modulus of asphalt or cement bound materials.
• Rutting.
• Roughness.
• Decrease in Friction.
• Surface wear (eg. caused by studded tyres).

All deterioration modules in PERS^® are linked through analytical process analysis.

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Seasonal variations, which affect the modulus of the different layers (as a function of temperature, moisture or freeze/thaw action), are user adjustable.

The different types of visual deterioration may be combined into a user defined Visual Rating Index.
The amount of surface and structural repair needs may also be calculated.

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When the cracking of bound layers reach a user defined level (in terms of decrease in modulus) the moduli of underlying unbound materials may be reduced due to ingress of moisture.

Dynatest International
rev. 050630-11