16.2.2 Geometrics for Divided Driveways

A raised or depressed separation between the entry and exit sides of a divided driveway needs to be visible to drivers. Suggested treatments and divider sizes are shown in
Table 16-3
.
Table 16-3: Dimensions for Dividers in the Driveway Throat to Separate Entry and Exit Sides of the Driveway
Treatment
Width
3
Length
Slightly raised
1
 (4-in) with contrasting surface
4
2
 –15
20
Notes:
1. For Rural - Rounded edges, 30° to 45° slope. (See Figure 16-7).
2. 6-ft minimum for pedestrian refuge, measured from back of curb (desirable) or from nominal face of curb (minimum).
3. Measured from nominal face of curb.
Figure 16-7
illustrates a slightly raised divider (height ≥ 4 inches).
Illustration of Slightly Raised Divider ( click in image to see full-size image)
Figure 16-7: Illustration of Slightly Raised Divider
A divided driveway is desirable in the following situations:
  • There is a total of four or more entering and exiting lanes; or
  • A large number of pedestrians (30 or more in a one-hour interval) routinely cross the driveway.
Locating appropriate signing (refer to the
TMUTCD
) and lighting within a divider may assist approaching drivers in determining the driveway’s location and geometrics.
An excessively wide divider may confuse drivers and cause them to think there are two closely spaced, two-way driveways. To avoid this problem, the
recommended maximum width of a divider is 15-ft
. On the other hand, a divider that is too narrow may not be adequately visible to the motorist. Therefore, the recommended
minimum width of a slightly raised divider (height ≥ 4-in) is 4-ft and 6-ft for a Pedestrian Refuge.