A deflector should be installed with approximately 3 inches of belting above the road surface. The design is simple and works well on low volume and low maintenance roads. The cost for an installed deflector is equivalent to that for an open top culvert. Because there is no abrupt grade change, water deflectors can be used on grades over 10 percent. On roads where farm equipment may have some trouble negotiating broad-based drainage dips, water deflectors would pose no difficulty.
Care is needed when using a road grader to maintain a road with deflectors.
Unless the grader operator is careful, the rubber belting can easily be sheared off. This is especially common during winter when the roads are snow covered. Open top and pole culverts can be used in place of any of the above-mentioned road drainage methods except outsloping. They work well when maintained, but are easily filled with sediment and rendered ineffective within a short period of time when not maintained. Open top and pole culverts are not recommended for crossing live or intermittent streams, and should not be used in lieu of pipe culverts.