Longitudinal and Transverse (L&T) Cracking

Longitudinal cracks are parallel to the pavement's center line or lay down direction. They may be caused by (1) a poorly constructed paving lane joint, (2) shrinkage of the AC surface due to low temperatures or hardening of the asphalt, or (3) a reflective crack caused by cracks beneath the surface course, including cracks in PCC slabs (but not at PCC joints). Transverse cracks extend across the pavement at approximately right angles to the pavement's center line or direction of lay down. They may be caused by (2) or (3). These types of cracks are not usually load associated. If the pavement is fragmented along a crack, the crack is said to be spalled.

Severity	Distress Example	Description
Low		Cracks have only light spalling (little or no FOD potential) or no spalling, and can be filled or nonfilled. If nonfilled, the cracks have a mean width of 1/4 in (6 mm) or less; filled cracks are of any width, but their filler material is in satisfactory condition. Porous Friction Courses: Average raveled area around the crack is less than 1/4 in (6 mm) wide.
Medium		One of the following conditions exists: (1) cracks are moderately spalled (some FOD potential) and can be either filled or nonfilled of any width; (2) filled cracks are not spalled or are lightly spalled, but filler is in unsatisfactory condition; (3) nonfilled cracks are not spalled or are only lightly spalled, but the mean crack width is greater than 1/4 in (6 mm), or (4) light random cracking exists near the crack or at the corners of intersecting cracks. Porous Friction Courses: Average raveled area around the crack is 1/4 in to 1 in (6 mm to 25 mm).
High		Cracks are severely spalled and pieces are loose or missing causing definite FOD potential. Cracks can be either filled or nonfilled of any width. Porous Friction Courses: Average raveled area around the crack is greater than 1 in wide (25 mm).