This article provides information to assist the designer in determining lane widths,
pavement cross slopes, shoulder widths, interchange cross-section elements, medians,
curbs, pedestrian facilities, and grading and side slopes. The number of lanes for a
given roadway facility is best determined using principles and procedures contained in
the “Highway Capacity Manual” (Ref. 10). This manual analyzes roadways to determine
an appropriate “level of service,” by which a letter value (A through F) is assigned
depending on the volume of traffic and other geometric features. Table 2.20 provides
a design guide for level of service for various facilities by functional classification and
terrain or locale. The table includes a brief description of the characteristics of each
level of service.