Q. Purpose of reinforcement in concrete roads?

The major purposes of reinforcement in concrete roads are:

(i)  To control the development and pattern of cracks in concrete pavement.

(ii) To decrease the spacing of joints. Generally joints and reinforcement in concrete structures are common design measures to cater for shrinkage and thermal movement. Therefore the inclusion of reinforcement enables the formation of tiny cracks in concrete pavement and this allows wider spacing of joints. 

Actually the amount of reinforcement in concrete slab isn't substantial and its contribution to structural strength of roads isn't significant. 

Fig: Road reinforcement