Open gutters can drain more water due to the larger possible depth and are less dependent on natural or artificial slopes. However, they cannot be cleaned with a standard road sweeper, and they can be an obstacle or a hazard for road users (prams, bicycles, etc.). This should be considered in the design phase.

You see this type of open gutters in Germany in areas with a natural slope in the landscape. Because of this they don’t need to be flushed.