00939810

Component

For the past 50 years, ever since the traffic assignment process became computerized, practitioners have struggled with lumpy loadings around centroid connectors. The problem stems from loading all of the trips from zone A to zone B via the same centroid connector. Practitioners have solved this problem for subarea studies by using the Focus or Window options. This process is now totally computerized for a subarea and/or for the entire region, resulting in enormous savings in modeling man-hours. The "b-node model" is new software that reads a metropolitan planning organization (MPO) zone-level network (in a format such as MINUTP) and trip table and performs a subzone capacity restrained traffic assignment. Subzones are created automatically by the software during execution. The b-node of each zone centroid connector, for a portion of or for all of the region, becomes a subzone; and each zone can have up to 12 centroid connectors. The program subdivides the zone trip table into this subzone system defined by the network. This is done in one of three ways: based on subzone land activity, based on equal splits among each subzone per zone or based on the reciprocal of the centroid connector's link time. The network is then updated by renumbering zones/subzones and nodes to prevent overlapping of nodes and subzones and to account for up to 10,000 subzones and finally the traffic assignment is made, all within one pass on the computer. This model is used extensively by the Virginia Department of Transportation (VDOT) for the Location & Design Section of VDOT for doing traffic forecasts for their design work. Little manual adjustments are needed with this subzone assignment output. All connecting link volumes are much smoother along a corridor than with traditional assignments using zone loadings only. The major problem with zone assignments has always been with the lumpiness around where centroid connectors tie into the network. Even turning movements are better, meaning that they match ground counts better than zone assignments. Every place where detailed link volumes are needed is better. Several examples including statistics comparing the results of the MPO zone level process versus the b-node subzone level process are presented. They include a study for an entire suburban jurisdiction (Loudoun County), corridor studies, subarea studies, and intersection studies. Loudoun County was subdivided into 1500 subzones from 145 MPO zones, while still carrying the rest of the region at zone level. The results of subdividing the entire Metropolitan Washington Council of Governments region of 2191 zones into subzones is also presented.

The CD-ROM contains the proceedings of the sixth, seventh and eighth conferences. The eighth conference proceedings were published in October 2001.

English

p. 273-281

2002

Eighth TRB Conference on the Application of Transportation Planning Methods

Figures (12) ; Tables (1)

Mathematical models; Traffic assignment; Traffic forecasting; Trip tables

Virginia Department of Transportation

Subzones

Loudoun County (Virginia)

Highways; Planning and Forecasting; I72: Traffic and Transport Planning

TRIS, TRB

Mar 21 2003 12:00AM

• A BEST PRACTICE TRUCK FLOW ESTIMATION MODEL FOR THE NEW YORK CITY REGION
• A PRACTITIONER'S ALGORITHM FOR QUASI-DYNAMIC TRAFFIC ASSIGNMENT
• ADDRESSING ENVIRONMENTAL JUSTICE (EJ) THROUGH COMMUNITY IMPACT ASSESSMENT (CIA)
• AN ANALYSIS OF TRAFFIC GROWTH RATES ON THE TEXAS-MEXICO BORDER
• CONGESTION PRICING AND ROADSPACE RATIONING: AN APPLICATION TO THE SAN FRANCISCO BAY BRIDGE CORRIDOR
• CORRIDOR SIMULATION STUDY FOR THE BRIDGE OF AMERICAS, EL PASO, TEXAS
• DEVELOPMENT OF AN ENVIRONMENTAL JUSTICE ANALYSIS METHODOLOGY FOR GEORGIA DEPARTMENT OF TRANSPORTATION'S MULTIMODAL TRANSPORTATION PLANNING TOOL
• ECONOMIC IMPACTS OF RAISED MEDIANS IN TEXAS: METHODOLOGY AND CASE STUDY RESULTS
• ENHANCING PUBLIC INVOLVEMENT THROUGH THE FULL UTILIZATION OF COMMUNICATIONS TECHNOLOGY
• FINANCING THE REGIONAL TRANSPORTATION PLAN: BALANCING EXPECTATIONS WITH FISCAL CONSTRAINT
• FLEXIBLE FUNDING: TRENDS AND POSSIBILITIES
• FLORIDA URBAN LAND USE ALLOCATION MODEL (ULAM)
• GIS APPLICATIONS USING DIGITAL ORTHOPHOTO DATA
• HIGHWAY ECONOMIC REQUIREMENTS SYSTEM FOR INDIANA: STATEWIDE PLANNING APPLICATIONS
• IMPLEMENTING THE LAND USE AND TRANSPORTATION POLICY IN OREGON'S 1999 HIGHWAY PLAN
• IMPROVED PLANNING DATA COLLECTION USING HANDHELD COMPUTERS
• LAND DEVELOPMENT AND ACCESS MANAGEMENT STRATEGIES FOR INTERCHANGE AREAS
• LESSONS LEARNED: ACCESS MANAGEMENT PROGRAMS IN SELECTED STATES
• MAKING LIFE EASIER FOR PLANNERS, ELECTED OFFICIALS, AND THEIR CONSTITUENTS: VISUALIZING THE INTERACTION OF TRANSPORTATION AND LAND USE
• MODIFICATIONS TO TRADITIONAL EXTERNAL TRIP MODELS
• ORIGIN AND DESTINATION ESTIMATION IN NEW YORK CITY USING AUTOMATED FARE SYSTEM DATA
• PROCEEDINGS OF THE EIGHTH TRB CONFERENCE ON THE APPLICATION OF TRANSPORTATION PLANNING METHODS, CORPUS CHRISTI, APRIL 22-26, 2001
• PROVIDING PUBLIC ACCESS TO TRANSPORTATION PROJECTS AND FUNDING WITH A VISUAL, INTERACTIVE TRANSPORTATION IMPROVEMENT PROGRAM
• PUBLIC INVOLVEMENT PLAN FOR THE KELLY PARKWAY CORRIDOR STUDY
• PUBLIC INVOLVEMENT: "DO YOU HAVE A 'POLICY' OR A 'PLAN'?"
• QUICKRIDE: THE KATY HOT LANE PROJECT IN HOUSTON
• RECENT EXPERIENCE WITH TIME OF DAY MODELING
• RECOMMENDED GUIDELINES FOR THE CALIBRATION AND VALIDATION OF TRAFFIC SIMULATION MODELS
• STATEWIDE PLANNING TOOL TO SUPPORT MULTIMODAL DECISION-MAKING
• SUBURBAN FIXED RAIL TRANSIT PLANNING IN NORTHERN VIRGINIA
• SURVEY DATA REPAIR USING HOT-DECK IMPUTATION PROCEDURE
• TCSP: DEVELOPING INNOVATIVE COMMUNITY BASED PLANNING TOOLS
• THE NORTHWEST ARKANSAS TRANSIT ASSESSMENT STUDY
• THE ROLE OF FIXED COMMITMENTS IN SHAPING ACTIVITY-TRAVEL PATTERNS
• THE TRIUMPH OF THE TRIVIAL MPO
• TRAFFIC FORECASTING TOOL (TFT): A GIS-BASED FORECASTING APPLICATION FOR THE INDIANA DEPARTMENT OF TRANSPORTATION
• TRANSPORTATION DECISION MAKING PROCESS
• TRAVEL DEMAND MODELING AND CONFORMITY DETERMINATION: THE ATLANTA REGIONAL COMMISSION CASE STUDY
• USING A TRADITIONAL TRAVEL DEMAND FORECASTING MODEL TO PERFORM VARIABLE PRICING ANALYSIS
• USING TRANSIMS IN TRANSPORTATION DECISION MAKING
• VALUE PRICING PROJECTS AROUND THE UNITED STATES