15 March 2001
DISTRESS 44, CORRUGATION
6.1. Description. Corrugation is a series of closely spaced ridges and valleys (ripples) occurring
at fairly regular intervals (usually less than 5 feet) (1.5 meters) along the pavement. The ridges
are perpendicular to the traffic direction. Traffic action combined with an unstable pavement
surface or base usually causes this type of distress. An illustration of corrugation is shown in
Figure 6.1. and an example is shown in Figure 6.2. Deduct curves for corrugation are shown in
6.2. Severity Levels.
6.2.1. L. Corrugations are minor and do not significantly affect ride quality (see measurement
6.2.2. M. Corrugations are noticeable and significantly affect ride quality (see measurement
6.2.3. H. Corrugations are easily noticed and severely affect ride quality (see measurement
6.3. How to Measure. Corrugation is measured in square feet (square meters) of surface area.
The mean elevation difference between the ridges and valleys of the corrugations indicates the
level of severity. To determine the mean elevation difference, a 10-feet (3-meter) straightedge
should be placed perpendicular to the corrugations so that the depth of the valleys can be
measured in inches (millimeters). The mean depth is calculated from five such measurements.