Spatial Resolution in SANDAG Activity-Based Model: How Much More Detail Is Enough? 15th TRB National...

Spatial Resolution in SANDAG Activity-Based Model:

How Much More Detail Is Enough?

Spatial Resolution in SANDAG Activity-Based Model:

How Much More Detail Is Enough?

15th TRB National Transportation Planning Applications Conference, Columbus OH

May 18th, 2015

Wu Sun, Gregor Schroeder & Matt KeatingSan Diego Association of Governments (SANDAG)

BackgroundBackground

SANDAG Activity-Based Model (ABM) and Active Transportation (AT) Model

ABM/AT model applications Spatial resolution in models

2

Enhanced ABM

CTM

Trans. SystemTrans. Policy

Traffic Assignment

SystemPerformance

Environmental Impact

EconomicAnalysis

3

LU Models

Integrated ABM & AT ModelIntegrated ABM & AT Model

Special Models

bicycle & Ped Route Choices

Improved NM Impedance

Improved Mode Choices

AT Model

Spatial ResolutionSpatial Resolution

4

• MGRA (gray lines)

• 23002 MGRA

• 4996 TAZs

MGRA: Master Geographic Reference Area (Grey Lines)TAZ: Transportation Analysis Zone (Orange Line)

What Are Affected by Spatial Resolutions?

What Are Affected by Spatial Resolutions?

Land use inputs Synthetic population Non-motorized impedances

– MGRA-MGRA walk– MGRA-MGRA bike

Transit impedances– MGRA-TAP walk

Highway impedances?

5

Vary by scenario

A Base ScenarioA Base Scenario

Path between zone 1 and 2 Path between zone 1 and 2

11

22

A Scenario with Smaller ZonesA Scenario with Smaller Zones

Path between zone 1 &1a and 2 Path between zone 1 &1a and 2

11

22

1a1a

How Spatial Resolutions Affect the Model?

How Spatial Resolutions Affect the Model?

Demand side– Location choices: tour, trip, and parking locations– Other choices?

Supply side– Skimming: walk, bike, transit, and highway.– Highway assignment?– Transit assignment?

8

Result AnalysisWalkability

Result AnalysisWalkability

9

Base Small Zones

6500000

7000000

7500000

8000000

8500000

9000000

9500000

Base Small Zones

100000

105000

110000

115000

120000

125000

130000

135000

Walkable zone pairs Walkable zone-TAP pairs

Result AnalysisAvg Walk Distance Btw Zones

Result AnalysisAvg Walk Distance Btw Zones

10

Avg_Walk_Dist Avg_WalkTransit_Dist0.50

0.70

0.90

1.10

1.30

1.50

1.70

1.90

2.10

BaseSmall Zones

Result AnalysisAvg Bike Distance Btw Zones

Result AnalysisAvg Bike Distance Btw Zones

11

Base Small Zones0

2

4

6

8

10

12

14

16

18

Result AnalysisTrips by Mode

Result AnalysisTrips by Mode

12

  Trips Mode Shares

Mode Base Small Zones Diff Base (%)Small Zones (%) Diff %

Auto 8,944,716

8,938,479 -6237 85.40 85.35 -0.06%

Walk 1,063,005

1,065,769 2764 10.15 10.18 0.27%

Bike 101,848

114,498 12650 0.97 1.09 12.43%

Walk to Transit

202,856

192,762 -10094 1.94 1.84 -4.96%

Other Transit

19,506

19,410 -96 0.19 0.19 -0.48%

Other 142,582

142,384 -198 1.36 1.36 -0.13%

Total 10,474,513

10,473,302   100.00 100.00 

Result AnalysisAvg Walk Trip Distance

Result AnalysisAvg Walk Trip Distance

13

Avg_Walk_Dist Avg_WalkTransit_Dist0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

BaseSmall Zones

Result AnalysisAvg Bike Trip Distance

Result AnalysisAvg Bike Trip Distance

14

Base Small Zones2.05

2.10

2.15

2.20

2.25

2.30

2.35

2.40

ConclusionsConclusions

• Finer spatial resolution• Improve walkability• Non-motorized trips increase and auto trips

decrease• Impact on bike trips more significant than on

walk trips

• How much more detail is enough?• What is important to you?• Other things to consider

15

Questions?Questions?

Contact: Wu Sun 619-6995757 Wu.Sun@sandag.org