14.8.2 Design Considerations

The distance between the MUT crossovers is central to the proper functioning of the intersection. The AASHTO recommended spacing from the main intersection to the median opening is 400-ft to 600-ft, although this distance may be modified per guidance in the
FHWA Median U-Turn Intersection Informational Guide
. Longer distances are preferred for weaving, but as the distance between the intersection and median opening increases, the delay for the minor road left-turn and through vehicles increases. See
Figure 14-32
through
Figure 14-34
for spacing considerations.
Spacing Consideration for a Major Street Left-Turn Movement ( click in image to see full-size image)
Figure 14-32: Spacing Consideration for a Major Street Left-Turn Movement
Source: FHWA MUT Informational Guide
Spacing Consideration for Minor Street Left-Turn Movement ( click in image to see full-size image)
Figure 14-33: Spacing Consideration for Minor Street Left-Turn Movement
Source: FHWA MUT Informational Guide
Spacing consideration for a Right-turn ( click in image to see full-size image)
Figure 14-34: Spacing consideration for a Right-turn
Source: FHWA MUT Informational Guide
The MUT median width is a function of the design vehicle (typically a WB-62TX or WB-67) and the preferred alignment of the design vehicle as it turns into the opposing traffic. See
Chapter 13
discussion on Median U-Turn Movements and minimum median width needed. For instances where the U-turn can’t be completed, a loon may be used to provide additional space. See
Figure 14-35
as an example application for a longer weaving distance.