Chapter 7F. Grade-Separated Crossings
Grade-separated crossings may be used to physically separate the crossing of school pedestrian traffic and vehicular flow.
Grade-separated crossings may be either overpasses over the highway or underpasses under the highway.
The design should follow the guidelines given in the published policies of the American Association of State Highway and Transportation Officials, such as "A Policy on Geometric Design of Highways and Streets" (see Section 1A.11).
Experience has shown that overpasses are more satisfactory than underpasses for pedestrian crossings, as overpasses are easier to maintain and supervise.
If use of the grade separation will be less convenient to pedestrians than an at-grade crossing, barriers or supervision should be considered to assure a satisfactory level of use.