00732384

Component

https://doi.org/10.3141/1555-08

http://scholar.google.com...dran&publication_year=1996

The 1994 update of the "Highway Capacity Manual" (HCM) includes a planning procedure to estimate the capacity condition of a signalized intersection (Xcm). The planning method results can also be extended to a planning application of the more data-intensive HCM operational procedure to estimate intersection critical flow-to-capacity ratio (Xc) and level of service with only planning-level data. Both the planning procedure and the planning application of the operational procedure involve default adjustment factors and synthesized traffic signal timing (called the "default signal timing"). Data from 166 Missouri intersections were used to determine how well the planning approaches predict operational analysis results. In general, the default signal timings had shorter cycle lengths than the timing plans used at pretimed signals. The shorter cycle lengths led to slightly higher flow-to-capacity ratios, since a higher proportion of each cycle was devoted to lost time. The default signal timings also had more equal flow-to-capacity ratios within critical lane groups. The shorter cycle lengths and more equal flow-to-capacity ratios led to a predicted level of service that was the same or better than that calculated for actual conditions. For the subject intersections, locally calibrated default adjustment factors yielded better predictions of flow-to-capacity ratios and level of service than the HCM defaults. The planning value for Xcm was often less than the actual Xc for operational analysis of actual conditions. This was to be expected since Xcm is based on the maximum allowable cycle length. The HCM planning procedure is expected to receive wide use in a variety of planning and design applications. Calibration of appropriate local default values should improve the accuracy of the planning procedure results.

This paper appears in Transportation Research Record No. 1555, Highway Capacity Analysis for Interrupted and Uninterrupted Flow Facilities.

English

p. 59-64

1996

Transportation Research Record

0309059526

Figures (4) ; References (6) ; Tables (9)

Adjustment factors; Alternatives analysis; Estimating; Field studies; Highway capacity; Intersections; Level of service; Operations; Planning; Signalized intersections; Traffic signal timing

Highway Capacity Manual

Field data; Intersection capacity; Operational analysis

Administration and Management; Highways; Operations and Traffic Management; Planning and Forecasting; I71: Traffic Theory

TRIS, TRB

Feb 13 1997 12:00AM

• ACCOUNTING FOR NONRANDOM ARRIVALS IN ESTIMATE OF DELAY AT SIGNALIZED INTERSECTIONS
• ANALYSIS OF TRAFFIC OPERATIONS AT ALL-WAY STOP-CONTROLLED INTERSECTIONS BY SIMULATION
• ASSESSING HEAVY VEHICLE IMPACTS ON OPERATION OF RURAL AT-GRADE INTERSECTIONS IN BRAZIL
• CAPACITY AT UNSIGNALIZED TWO-STAGE PRIORITY INTERSECTIONS
• ESTIMATING INTERSECTION APPROACH DELAY USING 1985 AND 1994 "HIGHWAY CAPACITY MANUAL" PROCEDURES
• EVALUATING WEAVING SECTION DESIGNS USING INTEGRATION
• ONE-SIDED WEAVING OPERATIONS ON ONE-WAY FRONTAGE ROADS
• OVERFLOW DELAY MODEL FOR SIGNALIZED ARTERIALS
• PHASE TIME PREDICTION FOR TRAFFIC-ACTUATED INTERSECTIONS
• PROGRESSION FACTOR FOR QUEUE LENGTH AND OTHER QUEUE-RELATED STATISTICS
• SATURATION FLOW AND CAPACITY OF SHARED LANES: COMPARATIVE EVALUATION OF ESTIMATION METHODS
• STOCHASTIC MODELING OF SHARED-LANE LEFT-TURN PROCESS AND ITS EFFECT ON SATURATION FLOW
• TRUCK PERFORMANCE ON ARGENTINEAN HIGHWAYS
• VARIABILITY OF SPEED-FLOW RELATIONSHIPS ON GERMAN AUTOBAHNS