Between the chalk downs of Woodingdean and the coastal gravels of Hove, subgrade strength can change within a single project. A pavement design that works on the well-drained flint gravels near the seafront may fail on the weathered chalk putty found just two miles inland. The Laboratory CBR test gives a direct measurement of that bearing capacity under controlled moisture and density conditions. We run both soaked and unsoaked procedures to reflect what happens after a wet Brighton winter when groundwater rises through the chalk fissures. For road reconstructions along the A23 corridor or car park expansions on the city fringe, the CBR road design methodology ties these lab values directly to pavement layer thickness, and we often pair results with Proctor tests to establish the compaction reference density for the same material.
A single CBR value can halve or double the required pavement thickness in Brighton, where subgrade conditions shift from chalk to gravel within a few hundred metres.
