What is the role of outlet pipes in bridge drainage systems?

Answer: B — To lead water away from the drain

The role of outlet pipes in bridge drainage systems is primarily to lead water away from the drain. Effective drainage is crucial for maintaining the integrity of bridge structures, as standing water can lead to deterioration over time. Outlet pipes are designed to channel water away from the bridge and its supporting structures, preventing pooling that could contribute to erosion, corrosion, or structural damage. These pipes ensure that water is efficiently transported away from the bridge and surrounding areas, thereby minimizing potential water-related issues. Properly functioning outlet pipes help in managing stormwater runoff and protecting the bridge from adverse environmental influences. This role is particularly important in areas subject to heavy rainfall or where snowmelt occurs, as swift drainage can greatly reduce the risk of flooding around the bridge. The other options reflect different functions that do not align with the primary objective of outlet pipes in a drainage system. For instance, retaining water could undermine the very purpose of these systems, while filtering debris and collecting rainfall are roles associated with other components of a drainage system, such as catch basins or sediment traps.