HCM Chapter 18

Urban Street Segments

Estimate free-flow speed, travel speed, stop rate, and level of service for one direction of travel on an urban street segment.

Open in Builder Takes this segment to the facility builder as a one-segment Chapter 16 facility. It arrives between two boundary signals with its own travel speed and LOS unchanged, and gains the facility aggregation over that one segment.
Scope. The compute engine is boundary-validated against HCM Chapter 30, Example Problem 1 (Exhibits 30-26 through 30-36), which the page defaults reproduce, and against all three access-point delay sources the method allows. The page itself is in beta pending final inspection. Verify results independently before relying on them in engineering work, and please report discrepancies on GitHub.

Segment

The subject direction of travel runs left to right between the two boundary intersections. In the 2D view the through demand and the access-point counts can be edited directly on the diagram.

← Opposing direction of travelSubject direction of travel →1,800 ft between boundary intersectionsUpstream boundaryDownstream (signalized)
Opp. access pts
Subj. access pts
Through demand veh/h

Plan view of the segment between its boundary intersections, drawn from the geometry inputs. Driveway positions are spaced evenly for legibility; the method uses only the counts. Animated traffic slows as segment LOS worsens. An illustration, not a simulation.

Geometry

Cross-section and access characteristics of the segment in the subject direction.

ft

Stop line to stop line.

ln
mph
ft
ft
%
%
pts
pts
%

Use 0 for a full restrictive median with no openings.

ft
mph

Traffic

Demand flow rates in the subject direction of travel.

veh/h

At the downstream boundary intersection.

veh/h

Access-Point Turning Delay

The Σ d_ap,i term of Equation 18-7, the delay through traffic suffers from vehicles turning at midsegment access points.

The three sources the method allows. The computed procedure (Equations 30-31 through 30-68) derives each per-point delay from the approach turn volumes, lane configuration, and opposing flow.

s/veh

One value per active access point, comma separated. The defaults are the Exhibit 30-35 published values for Example Problem 1.

Downstream Boundary Intersection

Control type and the through-movement performance inputs from the intersection analysis.

s/veh

From the Chapter 19, 21, or 22 analysis of the intersection.

veh/h

Needed for the volume-to-capacity ratio and the LOS F check.

s
s

Blank gives uniform arrivals, P = g/C. Use 1.333 for favorable progression.

veh/h/ln
stops/veh

Supply a value from an HCM computational engine. Unsignalized boundaries use the HCM defaults when blank.

%

Used by the traveler perception score.

Outputs

Results populate after pressing Calculate.

Base Free-Flow Speed (mi/hr):
Free-Flow Speed (mi/hr):
Access-Point Delay (s/veh):
Segment Running Time (s):
Segment Running Speed (mi/hr):
Through Delay (s/veh):
Travel Speed (mi/hr):
Full Stop Rate (stops/veh):
Spatial Stop Rate (stops/mi):
Volume-to-Capacity Ratio:
Traveler Perception Score:

Segment LOS: