Approach slab or transition slab, a reinforced concrete slab located between a roadway and bridge abutments or culverts or behind a retaining wall to permit a smooth transit of traffic is designed.

Design and detailing of approach slabsApproach slabs are designed for vehicle live load and dead load assuming they are simplysupported with a span of 0.9 times length. Approach slabs are then detailed to provide fixity atthe support, but allowing rotation without concrete spalling of the slab or support.

One side of the bridge deck joints is fixed to the approach slab, and the type of deck jointshould have capacity for rotation and vertical movement (uplift) compatible with expectedsettlement of the approach slab.

The design provides adequate lateral clearances from other parts of the structure (e.g. fromwing walls) to allow settlement of approach slabs. The gaps between approach slabs and wingwalls are sealed to prevent entry of drainage water.

A bedding layer consisting of 150 mm of compacted crushed rock is used under approach slabs,and an edge beam or additional reinforcement is used on the transverse free edge.

DrainagePavement settlement is a common problem at the end of approach slabs due to the entry of water inthe interface between the pavement and approach slab. A sub-surface drain should be installed atthis location unless specified otherwise.