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

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

Define mid block points

•On the main road

•Average 3-5 block points for each zone

•Action buffer

Distribution of mid block points

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) Mid block-based traffic assignment

Experimental Results (cont’d) Zone-based traffic assignment

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

Thank You!

Open for Questions...