HCM Chapter 21

All-Way STOP-Controlled Intersections

Estimate departure headways, control delay, queues, and level of service for each lane and approach at an all-way STOP-controlled intersection.

The compute engine reproduces the published HCM worked examples for this chapter, including the iterative departure-headway convergence of the Chapter 21 method. Verify results independently before relying on them in engineering work, and please report discrepancies on GitHub.

Intersection

The picture follows the approach lane counts below. Hover the legend to highlight an approach, and in the 2D view single-lane approach volumes can be edited directly on the diagram.

STOPSTOPSTOP
EB
WB
SB

Every approach stops. An approach with zero lanes removes its leg, matching the three-leg worked examples. Animated traffic slows and bunches with each approach LOS after a run. An illustration, not a simulation.

Eastbound (EB) Approach

Lanes in left-to-right order with the demand volume assigned to each. Set lanes to 0 for a leg with no approach.

%
veh/h
veh/h
veh/h

Westbound (WB) Approach

Lanes in left-to-right order with the demand volume assigned to each. Set lanes to 0 for a leg with no approach.

%
veh/h
veh/h
veh/h

Northbound (NB) Approach

Lanes in left-to-right order with the demand volume assigned to each. Set lanes to 0 for a leg with no approach.

%

Southbound (SB) Approach

Lanes in left-to-right order with the demand volume assigned to each. Set lanes to 0 for a leg with no approach.

%
veh/h
veh/h
veh/h

Traffic

Peaking characteristics shared by all approaches.

Leave blank if the lane volumes are already peak 15-min flow rates.

h

Outputs

Results populate after pressing Calculate.

LaneFlow Rate (veh/h)Departure Headway (s)Utilization xDelay (s/veh)LOS95% Queue (veh)
Intersection Delay (s/veh):

Intersection LOS: