HMA overlays have also been used on structurally deficient CPCD. However, the success of those overlays has been marginal to poor because they are an expensive treatment with a relatively short service life. CPCD that has experienced pervasive transverse contraction joint failures with faulting require thicker HMA. As a rule of thumb, reflective cracking progresses at a rate of 1 in. per year. The loss of load transfer at the transverse joints results in independent movement of the CPCD slabs, which causes a crack to form in the HMA that reflects through to the surface. HMA spalls from either side of the joint. If the joint in the CPCD is open wide enough, two cracks will reflect through, one from each side of the joint. Large pieces of HMA can break off and leave an opening above the joint. Rubblization of the existing concrete pavement combined with a thick HMA overlay has also been a successful rehabilitation technique. However, once the existing PCC pavement has been rubblized, it no longer behaves like a rigid pavement and can no longer be considered a rigid pavement. Rehabilitation designs using this technique should use a flexible pavement approach.