HCM Chapter 23

Ramp Terminals and Alternative Intersections

Estimate experienced travel time and level of service by origin-destination movement and for the facility as a whole, for signalized diamond interchanges (Part B) and for RCUT, MUT, and DLT alternative intersections (Part C).

The compute engine reproduces the published HCM Chapter 34 example problems within the library's documented tolerances: the conventional diamond, the diverging diamond, the Parclo A-2Q, and the single-point urban interchange with pretimed signals under Part B, and the STOP-controlled RCUT, the MUT, and the DLT evaluations under Part C. The other five partial cloverleaf forms of Exhibit 23-17 (A-4Q, AB-2Q, AB-4Q, B-2Q, B-4Q) are supported by the engine but have no published example problem behind them, so they are not offered here. Verify results independently before relying on them in engineering work, and please report discrepancies on GitHub.

Analysis Part

Part B evaluates signalized interchange ramp terminals. Part C evaluates alternative intersections: the restricted crossing U-turn, median U-turn, and displaced left-turn.

Interchange Configuration

Signal timing and geometry shared by both ramp terminal intersections. The arterial runs east-west, with the southbound ramps at the west intersection and the northbound ramps at the east intersection.

Switching loads that form's published example as defaults.

s
ft
pc/h/ln
s
%
%
ft

Applied with a positive sign to left turns and a negative sign to right turns.

mph

Interchange

O-D movements per Exhibit 23-8. Hover the legend to isolate a group; demands are editable on the 2D picture, and the traffic animation slows per O-D LOS after a run.

NB
SB
EB
WB

O-D letters follow Exhibit 23-8: off-ramp lefts and rights, arterial turns onto the on-ramps, and the arterial throughs. Editors hold each group's O-D demands in letter order. Animated traffic slows per O-D LOS after a run. An illustration, not a simulation.

Origin-Destination Demands

Hourly demand volumes for the fourteen O-D movements of HCM Exhibit 23-20. Frontage-road and U-turn movements are usually 0.

veh/h
veh/h
veh/h
veh/h
veh/h
veh/h
veh/h
veh/h
veh/h
veh/h
veh/h
veh/h
veh/h
veh/h

Lane Groups and Green Times

Lanes and displayed green interval for each interchange lane group. Green begin times are measured from the start of the common cycle and may wrap past the end of the cycle.

Lane GroupLanesGreen Begin (s)Green Duration (s)
EB external through + right
EB internal through
EB internal left (to NB on-ramp)
WB external through + right
WB internal through
WB internal left (to SB on-ramp)
NB off-ramp left
NB off-ramp right
SB off-ramp left
SB off-ramp right

Outputs

Results populate after pressing Calculate.

O-D MovementDemand (veh/h)Control Delay (s/veh)EDTT (s/veh)ETT (s/veh)LOS
Interchange Experienced Travel Time (s/veh):

Interchange LOS: