Section 3(3)(iii) in Kerala Highway (control of access and restriction on use of land) Rules, 2000
(iii)A concrete or rubble masonry drain shall be constructed across the approach at the extreme end of the highway land and shall have a minimum opening of 60 cm x 60 cm and the drain shall be covered by a reinforced concrete slab of 18 cm minimum thickness or as may be necessary. Alternatively the drain may be constructed using non-pressure concrete pipes of 75 cm or more internal diameter.