The geometric design of railroad-highway grade crossings should be made jointly when determining the warning devices to be used. When only passive warning devices are used, such as signs and pavement markings, the roadway drivers are warned of the crossing location but need to determine for themselves whether there are train movements for which they should stop. On the other hand, when active warning devices such as flashing light signals or automatic gates are used, the driver is given a positive indication of the presence or the approach of a train at the crossing. Many significant variables should be considered in determining the type of warning device to be installed at a railroad-grade crossing. For certain low-volume roadway crossings, where adequate sight distance is not available, additional signing may be needed.

Traffic control devices for railroad-highway grade crossings consist primarily of signs, pavement markings, flashing light signals, and automatic gates. Criteria for the design, placement, installment, and operation of these devices, refer to the , as well as the use of various passive warning devices.

Some of the considerations for evaluating the need for active warning devices at a grade crossing include the type of roadway, volume of vehicular traffic, volume of railroad traffic, maximum speed of the railroad trains, permissible speed of vehicular traffic, volume of pedestrian traffic, crash history, sight distance, and geometrics of the crossing. The potential for complete elimination of grade crossings without active traffic control devices (e.g., closing lightly used crossings and installing active devices at other more heavily used crossings) should be given prime consideration.

These guidelines are not all-inclusive. Situations not covered by these guidelines should be evaluated using good engineering judgment. Additional information on railroad-highway grade crossings can be found in the following sources:

Numerous index formulas have been developed to assess the relative conflict potential at railroad-highway grade crossings based on various combinations of its characteristics. Although no single formula has universal acceptance, each has its own values in establishing an index. When used with sound engineering judgment, each formula provides a basis for a selection of the type of warning devices to be installed at a given crossing.

The geometric design of a railroad-highway grade crossing involves the elements of alignment, profile, sight distance, and cross-section. The appropriate design may vary with the type of warning device used. Where signs and pavement markings are the only means of warning, the roadways should cross the railroad, at or nearly at, right angles. Even when flashing lights or automatic gates are used, small intersection angles should be avoided. Regardless of the type of control, the roadway gradient should be flat at, and adjacent to, the railroad crossing to permit vehicles to stop when necessary, and then proceed across the tracks without difficulty.