Roads are the main transportation system in any country and, therefore, must be maintained in good physical condition to provide a safe and seamless flow to transport people and goods.
However, road pavements are subjected to various defects because of construction errors, aging, environmental conditions, changing traffic load, and poor maintenance. Regular inspections are therefore
recommended to ensure serviceability and minimize maintenance costs. Ground-penetrating radar
(GPR) is a non-destructive testing (NDT) technique widely used to inspect the subsurface condition
of road pavements. Furthermore, the integral use of NDTs has received more attention in recent years
since it provides a more comprehensive and reliable assessment of the road network.

Accordingly, GPR has been integrated with complementary NDTs to extend its capabilities and to detect potential
pavement surface and subsurface distresses and features. In this paper, the non-destructive methods
commonly combined with GPR to monitor both flexible and rigid pavements are briefly described.
In addition, published work combining GPR with other NDT methods is reviewed, emphasizing the
main findings and limitations of the most practical combination methods. Further, challenges, trends,
and future perspectives of the reviewed combination works are highlighted, including the use of
intelligent data analysis