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Longitudinal cracks <br />Cracks running in direction of traffic are longitudinal cracks. Center line or lane line cracks are caused by <br />inadequate bonding during construction or reflect cracks in underlaying pavement. Longitudinal cracking <br />in the wheel paths indicates fatigue failure from heavy vehicle loading. Longitudinal cracks within one foot <br />of the edge are caused by insufficient shoulder support, poor drainage, or frost action. Cracks usually <br />start as hairline or very narrow (top left photo) and widen and erode with age (bottom right). Without crack <br />filling they can ravel, develop multiple cracks and become wide enough to require patching. <br />Filling and sealing longitudinal cracks will reduce moisture penetration and prevent further subgrade <br />weakening. Multiple longitudinal cracks in the wheel path or pavement edge indicate a need for <br />strengthening with an overlay or reconstruction. <br />Page 44 <br />Construction <br />joints <br />Left: centerline <br />crack (still tight) <br />Right: crack <br />between lane and <br />paved shoulder <br />(open about 1/4'9 <br />Wheel path and <br />edge cracking <br />Left: first stage of <br />wheelpath cracking <br />caused by heavy <br />traffic loads <br />Right: edge cracking <br />from weakened sub- <br />base and traffic loads <br />Advanced <br />cracking and <br />deterioration <br />Left: multiple open cracks <br />at center line, wheelpaths <br />and lane center <br />Right: multiple secondary <br />cracks and erosion <br />along center line <br />