An Experimental Procedure for Mid Block-Based Traffic Assignment on Sub-area with Detailed Road...
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Transcript of An Experimental Procedure for Mid Block-Based Traffic Assignment on Sub-area with Detailed Road...
An Experimental Procedure for Mid Block-Based Traffic Assignment
on Sub-area with Detailed Road Network
Tao YeM.A.Sc Candidate
University of Toronto
MCRI Student Caucus MCRI Student Caucus MeetingMeetingSeptember 13, 2003September 13, 2003
Outline
Background and Problem Statement Study Area and Data Resources Procedure and Methodologies Experimental Results Summary and Conclusions
Background and Problem Statement
Conventional zone-based model Zone-based: centroid to centroid Lack enough detail for intrazonal trips and
short trips (in GTA Model, 14% intrazonal trips are not included in the traffic assignment model)
Only 40% of the real road network in the GTA is included in the model
Not appropriate to provide accurate Origin-Destination trip matrices for input into emerging micro-simulation models of corridors or sub-networks
Objectives Develop an experimental procedure to
implement mid block-based (block: road link) traffic assignment on a detailed sub-area network Create mid block points to realistically represent trip
ends Develop mid block-based trip matrix Model the detailed network including all local streets Perform mid block-based traffic assignment Compare the results from mid block-based traffic
assignment and zone-based traffic assignment Data processing and network modeling---
ArcGIS8.2, Traffic assignment---EMME/2
Study Area --- Downtown Core (PD1)
Features (2001):
40.6 km2
64 traffic zones
86,900 households
164,200 residents
Data Resources From Data Management Group:
2001 Transportation Tomorrow Survey (TTS) 2001 EMME/2 GTA network model Traffic cordon counts in the study area
From Data, Map & Government Information Services: 2001 Ontario detailed street map (Shapefile format) 2001 Ontario land use map (Shapefile format) 1996 Canada census: enumeration area (Shapefile format) Building heights information from Statistics Canada (Shapefile) 2002 Toronto air photos linked from Toronto Public Library
(Jpeg)
Procedure and Methodology Step 1: Create a traversal matrix for the study area from
the GTA model
Step 2: Adjust the traversal OD matrix
Step 3: Define mid block points
Step 4: Estimate the production/attraction ratio for each mid block point Step 5: Redistribute zone-based trip matrix to mid block- based trip matrix
Step 6: Create sub-area detailed network model
Step 7: Perform mid block-based traffic assignment
Create Traversal Matrix Traversal Matrix (as used in EMME/2): An O-D matrix for
a sub-area or a ramp-to-ramp matrix for a freeway facility extracted from the total demand matrix
Identify and label all links entering and exiting from sub-area Run a traversal matrix traffic assignment in EMME/2
Inputs: Peak period auto-drive trip matrix retrieved from the 2001 TTS
data 2001 EMME/2 GTA Network Model
Outputs: A sub area network extracted from the GTA network An auto trip matrix consistent with the study area zone system,
considering all the GTA traffic flows
Traversal Matrix Adjustment Run the macro DEMADJ22 (a gradient approach) to
get the adjusted matrix traffic count screeline
Estimate Production/Attraction Ratio
Production ratio Based on the population size Census enumeration area population
Attraction Ratio Based on the floor space Three land use categories: commercial, governmental and
institutional, industrial and storage Assume 3-meter height as one floor layer
An example of the P/A ratio
Ratio in Traffic Zone
GTA2001_Zone Mid_Block_ID Production Attraction
201 1001 0 0.4
201 1183 0.35 0.2
201 1184 0.15 0.2
201 1186 0.5 0.2
Generate mid block-based trip matrix
njmiijmn APTT **
Where:
mnT ----- Trips from mid block m to mid block n;
ijT ----- Trips from zone i (where m belongs to) to zone j (where n belongs to);
miP ----- Production ratio for mid block m within traffic zone i;
njA ----- Attraction ratio for mid block n within traffic zone j.
Model a detailed network Mid block point
Obtain coordinates from ArcGIS
Base network Assume features for local street links: lane number---1,
free flow speed---40, and lane capacity---400.
Turn tables DMTI format: from link to link EMME/2 format: from node to node
Experimental Results Comparison of two network model features
GTA Zone-based Model Mid Block Model
Internal Zones/Mid Block points 64 238
External zones 35 35
Regular nodes 286 1617
Directional links 1416 4476
Turn table entries 208 717
Experimental Results (cont’d) Main road link volume analysis
Zone-based assignment Mid block-based Assignment
All links with counts 66 66
Link volume 0.82 0.88
Slope 1.36 1.31
Y intercept -150 -108
All turns with counts 48 48
Turn 0.79 0.85
Slope 1.28 1.15
Y intercept -35 -12
Experimental Results (cont’d) Local street volume analysis
Parameters
Number of local links 41
Link volume 0.65
Slope 0.80
Y intercept -34
Experimental Results (cont’d) Running time analysis
Zone-based Assignment Mid-block Assignment
Objective Function ngap * =0.1 ngap=0.1
No. Of Iterations 11 16
Total CPU time (seconds) 5.3 33.8
ngap: normalized gap, which is difference between the mean trip time (or cost) at the previous iteration and the mean minimal trip time (cost) computed by assigning the demand to shortest path of the current iteration.
Conclusions and Recommendations
Summary of benefits and values More realistic road network representation Suitable for data analysis of GPS-based personal travel surveys More precise results for traffic impact studies More accurate inputs for the traffic micro-simulation studies GTA model enhancement
Further research Combination of long trips and short trips --- windowed model Consideration of other measures to estimate production and
attraction ratio Enough traffic survey counts to conduct traversal matrix
adjustment