What aspect of pavement drainage is improved when installing edge drains during rehabilitation?

Installing edge drains during pavement rehabilitation primarily improves the removal of subsurface water from the pavement structure. Edge drains are typically installed along the edges of the pavement, adjacent to the shoulder, to intercept and drain water that has infiltrated the pavement layers or the subgrade. This water can weaken the pavement structure and contribute to distresses such as rutting, cracking, and potholes. Edge drains provide a pathway for this water to escape, preventing it from accumulating and causing damage. They consist of a perforated pipe or a geocomposite drain wrapped in a filter fabric to prevent soil particles from clogging the drain. The water collected by the edge drains is then discharged into a ditch or other drainage system. By effectively removing subsurface water, edge drains help to maintain the strength and stability of the pavement structure, extending its service life and reducing the need for future maintenance. Improved drainage reduces the likelihood of frost heave in cold climates, preventing damage from freeze-thaw cycles.