For US shippers struggling to secure truck capacity, now is the time to act, and the first thing they should think about is time, especially how much time is lost in their supply chains. Capacity most often is measured in drivers, tractors, trailers, containers – all physical assets, human or otherwise – and space, as in the amount of space available in a trailer or on a pallet. But the fourth dimension is capacity’s hidden dimension. Shippers facing concrete limits in physical capacity need to work with time to create capacity without adding assets.