Three-leg interchanges provide connection for three intersecting approach roadways. These interchanges should only be used after careful consideration because expansion to include a fourth leg is usually very difficult. If the potential exists that a fourth leg will ultimately be included, another type of interchange may be more appropriate.

The most widely used three-leg interchange is the trumpet, as shown in . This type of interchange is particularly suitable for the connection of a major facility and a freeway. Preference should be given to the major turning movements so that the directional ramps carry the higher traffic volume and the lower traffic volumes use the loop ramps.

Direct three-leg interchanges are those in which all movements are provided without the use of loops. These interchanges should be used only where all movements have high traffic volumes. Direct three-leg interchanges require more than one structure or, alternatively, a three-level structure. Both variations are illustrated in