15.7.8 Ramp Spacing
The minimum acceptable distance between ramps is dependent upon the merge, diverge, and weaving operations that take place between ramps, as well as distances required for signing.
The minimum distance is measured from painted nose of gore to painted nose of gore as illustrated in
.
The distance between successive ramps must be determined with the analysis procedures referred to in the
. A design waiver will be required if the minimum distance for the minimum Level of Service (LOS) as determined by an HCM analysis cannot be met. Additionally, a design waiver will be required if the minimum values in
cannot be met.When the distance between the successive painted noses of an entrance-exit (EN-EX) ramp combination is less than 2,000-ft on a freeway or 1,500-ft on a collector-distributor or frontage road, then speed-change lanes should be connected to provide an auxiliary lane.
When the minimum needed distance cannot be achieved, consideration should be given to consolidating or braiding the ramps in lieu of requesting a design waiver.
Ramp configurations shown in
are relative to the facility being traveled on.
See section 15.8.1 for additional considerations on ramp spacing along frontage roads.