Comparison of EMME Transit Assignment Methods Optimal Strategies vs Strategies with Variants (path assignment)

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Comparison of EMME Transit Assignment
MethodsOptimal Strategies vs Strategies with
Variants (path assignment)

• Karen TsangBureau of Transport Statistics
• Department of Transport
• May 2011

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Overview

• A series of transit assignment experiments
• ? Compare standard and new methods
• ? To understand how flows are distributed
• ? Using simplified network (2 transit services)
• ? Variables in-veh time, wait time, headway
• choice between centroid
  connectors
• Sydney Strategic Travel Model (STM) Network
• ? Rail Assignment Example

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Standard vs New
Current New Release
Module 5.31 5.32
Assignment Preparation 5.11 5.32
Option One option 1 Optimal Strategies no path file Two options 1 Optimal Strategies path file saved assignment results same as current if additional gc and variants inputs not specified 2 Strategies with Variants path file saved distribute flows based on frequency and transit time (optional) multiple paths at centroid connectors (optional)
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Standard vs New
Current New Release
Module 5.31 5.32
Assignment Preparation 5.11 5.32
Option One option 1 Optimal Strategies no path file Two options 1 Optimal Strategies path file saved assignment results same as current if additional gc and variants inputs not specified 2 Strategies with Variants path file saved distribute flows based on frequency and transit time (optional) multiple paths at centroid connectors (optional)
STANDARD
NEW
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Experiment 1

• Demand from origin to destination 100
  passengers
• No auxiliary (walk) link choice
• New service variables
• Headway 5, 10, 15 and 20 minutes
• Travel time 1 to 40 minutes in 1 min interval
  
• Percentage of passengers using New service?

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Experiment 1

• Assignment attributes and weighting factors
• In-vehicle time factor 1.0
• Auxiliary (walk) travel time factor 2.0
• Wait time factor 2.0
• Wait time Headway/ 2
• Boarding time 5 min
• Boarding time factor 1.0

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Experiment 1
STANDARD Distribution of flows based on
frequency
NEW Distribution of flows based on frequency and
transit time
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Experiment 2 Reduced wait time weight
Wait time weight 2.0 (Experiment 1) Wait time
weight 1.0 (Experiment 2)
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Experiment 2 Reduced wait time weight

STANDARD Wait time weight 1.0
STANDARD Wait time weight 2.0 Results from
Experiment 1
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Experiment 2 Reduced wait time weight

STANDARD Wait time weight 1.0 Flow distribution
based on frequency
NEW Wait time weight 1.0 Flow distribution
based on frequency and transit time
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Experiment 3 Choice between connectors

• Demand from origin to destination 100
  passengers
• Choice between 2 centroid connectors
• New service variables
• Headway 5, 10, 15 and 20 minutes
• Travel time 1 to 40 minutes in 1 min interval
  
• Percentage of passengers using New service?

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Experiment 3 Choice between connectors

STANDARD One service route is chosen All or
nothing
NEW Two centroid connector choices Option 2
(logit) Scale parameter 0.2 (default) where
exp(-scale transit time to destination)
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Experiment 3 Choice between connectors

STANDARD One service route is chosen All or
nothing
NEW Two centroid connector choices Option 2
(logit) Scale parameter 0.5 where exp(-scale
transit time to destination)
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Experiment 3 Choice between connectors

STANDARD One service route is chosen All or
nothing
NEW Two centroid connector choices Option 2
(logit) Scale parameter 0.8 where exp(-scale
transit time to destination)
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Experiment 3 Choice between connectors

STANDARD One service route is chosen All or
nothing
NEW Two centroid connector choices Option 2
(logit) Scale parameter 1.0 where exp(-scale
transit time to destination)
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Key Differences

• Distribution of flows to attractive lines
• Standard based on frequency
• New based on frequency and transit time
  (optional)
• Distribution of flows between connectors at
  centroids
• Standard one path with best generalised time
  (AON)
• New multiple paths at centroid
  connectors (optional)

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Experiment Results

• Flow Distribution on attractive lines
• Standard Step function
• New Step with transition logit curve
• Flow Distribution between multiple centroid
  connectors
• Standard AON
• New AON or multiple preferred paths

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Sydney Strategic Travel Model (STM)

• Rail Network

• Rail Stations
• Over 340
• Rail Transit Lines
• 80 (approx)
• Rail Link Length
• Approx 2400 km

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Sydney Strategic Travel Model (STM)

• Rail Line Example

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Sydney Strategic Travel Model (STM)
Rail Lines (Entire Network)
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STM Network - Rail Assignments

• Fixed Demand 3.5-hr rail AM demand
• Network Rail Network with walk and bus
  access/egress
• Assignment Methods
• Travel zone to Travel zone assignments
• Standard Assignment Optimal Strategies
• Strategies with Variants
• Path Saved
• Distribution of flows based on frequency and
  transit time
• Scale Parameter 0.5

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Rail Assigned Volumes
Method 1 Optimal strategies (standard)

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Rail Assigned Volumes
Method 2 Strategies with variants (new)

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Rail Assigned Volume Differences

• Green
• Less volumes in new method
• Red
• More volumes in new method

-6
4
1
4
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Conclusions Rail Assignment

• Rail assignment differences up to / 6
• Minimise back-tracking
• Retain fast assignment run time
• Standard 1 minute, New 2 minutes
• Increase attractiveness of express services