expressways,
freeways, or interstate highways with nonbarrier medians where space permits
and there is a need. U-turns may be needed for proper operation of police and emergency
vehicles, as well as for equipment engaged in physical maintenance, traffic service,
and snow and ice control. U-turn crossings should not be constructed in barrier-type
medians. When U-turn median openings are permitted, it is intended they be spaced
as close to 3-mi (4.8-km) intervals as possible. Crossings should be located at points
approximately 1000 ft (305 m) beyond the end of each interchange speed change
lane.
An example of a typical U-turn median opening is shown in Fig. 2.28, which indicates
geometric features applicable to crossings located in medians of widths ranging
from 40 to 84 ft (12 to 26 m). Turning radius should be modified proportionately for
medians of varying widths. Tapers should be 200 ft (61 m) in length for all median
widths. The profile grade line should normally be an extension of the cross slope of
the shoulder paving, rounded at the lowest point.