The CBR is a standard utilized when you know the sub-soil bearing characteristics and the type of traffic moving over a paving profile of asphaltic paving or concrete paving to come up with a design thickness for pavement and substrate.
Back in the day I had to do a CBR on the sub-base of an already paved school parking lot. It was 25 degrees in a howling wind with snow.
Had to core through the asphalt and mount the measurement gizmo against the bottom of a fully loaded dump truck. Took all day and ran into freezing water problems with the coring machine.
That was the one job that broke me of ever wanting to work outside again in that kind of weather.
The icing though was getting an almost free day having to drive 2 hours to another of our offices that had an engineer who could do the calculations.