Condition Rating Systems

Based on measurements of roughness, surface distress, skid resistance and deflection, pavements can be assigned a score that reflects their overall condition. This score, sometimes called a pavement condition rating, quantifies a pavement's overall performance and can be used to help manage pavement networks. By carefully choosing the rating scale (called the condition index), pavement condition scores can be used to (Deighton, 1998):

• Trigger treatment. Once a pavement's condition rating deteriorates to a certain level, it can be scheduled for maintenance or rehabilitation.
• Determine the extent and cost of repair. A pavement condition score is a numerical representation of a pavement's overall condition and can thus be used to estimate the extent of repair work and the likely cost.
• Determine a network condition index. By combining pavement condition scores for an entire road network, a single score can be obtained that gives a general idea of the network condition as a whole.
• Allow equal comparison of different pavements. Since a pavement condition score accounts for all types of pavement performance measures it can be used to compare two or more pavements with different problems on an equal footing.

A pavement condition index is simply the scale, or series of numbers, used to describe a pavement condition. Typical pavement condition indices may be based on a scale of 0 to 5 or perhaps 0 to 100. The proper pavement condition index depends upon the objectives of whatever system is used to manage a particular pavement network (called a Pavement Management System or PMS).

Present Serviceability Index (PSI)

The Present Serviceability Index (PSI), one example of a condition rating system, is a 0 to 5 scale that was originally based on a panel of raters who, between 1958 and 1960, rated various roads in the states of Illinois, Minnesota, and Indiana. PSI ranges from 5 (excellent) to 0 (essentially impassable), and is still used today throughout the country. It is often a good choice for a smaller, less sophisticated pavement rating system.