Forensic investigations were conducted to identify the causes of longitudinal cracking (LC) of a newly constructed highway. The case-study highway was built with a composite pavement system and is located in a semiarid region north of the equator in Africa. During these investigations, several tests were performed, such as a visual survey of cracks, nondestructive tests, and coring. Long-term observations of soil movements and crack growth were executed. The results showed that the main reasons for surface cracking were (1) use of clayey soils as filling material, and (2) the region’s climate. Such conditions led to a cycle of nonuniform swelling-shrinkage of embankment soil, which resulted in failure of the treated base and the beginning of a well-defined cracking mechanism. The results of this investigation will allow suggestions to be proposed for immediate improvement of the zone against most defects and to implement remedial solutions for other parts.