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Trip Generation for
Smart Growth
Christine Eary, SANDAG April 15, 2012
2
San Diego Jurisdictions
Oceanside
Carlsbad
Encinitas
Solana Beach Del Mar
San Diego
Coronado
Imperial Beach
Chula Vista
National City
Lemon Grove
La Mesa El Cajon
Santee
Poway
Escondido San
Marcos
Vista
County of San Diego
San Diego
Riverside County
Imperial County
MEXICO
PACIFIC OCEAN
Orange County
3
San Diego Regional Comprehensive Plan
Urban Form
Transportation
Housing
Healthy Environment
Economic Prosperity
Public Facilities
Borders
Adopted by SANDAG in 2004
4
Smart Growth Tool Box
Planning Tools
• Smart Growth Concept Map
• I-PLACE3S Sketch Model
• Visualization Tools and
Smart Growth Photo Library
• Smart Growth Design Guidelines
• Trip Generation/Parking Study
• San Diego Regional Bicycle Plan
• Public Outreach Program
Financing Tools
• TransNet Smart Growth
Incentive Program
• TransNet Environmental
Mitigation Program
• TransNet Active
Transportation Grant
Program
5
Smart Growth
Concept Map
Study Purpose
• Supplement existing
published rates
• Provide data for smart
growth development
and planning in San
Diego region
Site Selection – TOD/MXD
• Visited 30+ sites
• Sites were initially selected based on input from SANDAG staff, member agencies, and Project Team
• 6 sites chosen
Site #1 - Rio Vista Trolley Station
Promenade
San Diego
Rio Vista Promenade, San Diego 9
Site #2 – La Mesa Village Plaza
La Mesa
La Mesa Village Plaza, La Mesa 11
Site #3 - Uptown District
San Diego
Uptown District, San Diego 13
Site #4 – The Village @ Morena Vista
San Diego
The Village at Morena Vista, San Diego 15
Site #5 - Hazard Center
San Diego
Hazard Center, San Diego 17
Site #6 – Otay Ranch
Chula Vista
Otay Ranch Heritage Town Center, Chula Vista 19
20
Smart Growth
Concept Map
Site Selection – SANDAG SGOAs
(Smart Growth Opportunity Areas)
• List of 57 SGOAs chosen
• Counts not possible (too big)
• 20 of those had at least 100 trip records in household survey
• Comparison of trip reduction percentages between these sites and MXD model
MXD Model Validation – SGOAs
Figure 1
Net Vehicle Trip Reduction - Sites with >100 Survey
Records
0%
10%
20%
30%
40%
50%
60%
70%
80%
0% 20% 40% 60% 80%
Estimated
Ob
serv
ed
MXD method tends
to be conservative,
more likely to
underestimate
internalization
Study Adoption
• Change is scary, change is hard.
• Parking confused things
• Now incorporated into traffic impact study
data requests at SANDAG
• Traffic impact study guidelines next
Study URL
http://www.sandag.org/tripgeneration
Questions?
- Christine Eary, SANDAG
- Jerry Walters, Fehr & Peers
- Richard Lee, Fehr & Peers
Capturing the Transportation
Benefits of Mixed Use Development
APA National Planning Conference
April 2012
Jerry Walters ◊ Fehr & Peers
1. Density dwellings, jobs per acre
2. Diversity mix of housing, jobs, retail
3. Design connectivity, walkability
4. Destinations regional accessibility
5. Distance to Transit rail proximity
6. Development Scale pop, jobs
7. Demographics household size, income
8. Demand Management pricing …
“D” Factors that Reduce Trips and VMT
1D
Typical 4-Step Model “Blind Spots”
Reality Model’s View
Circulation Network
Walking Environment
Density, Clustering
7D Analysis of Travel Survey Data
• Statistical relationships from travel data for sites meeting ITE multi-use definition
• Assess influence of 7D’s, mix and scale
• Validate through comparison to field data
239 MXD: Seattle, Portland, Sacramento, Boston, Atlanta, Houston Validation: Northern and So. Cal, Texas, Georgia, Florida, Utah
Gateway Oaks, Sacramento River Place, Portland
Nationwide Survey of Mixed-Use Travel
• Density of population and employment
• Diversity: jobs/housing relative to regional balance • Diversity: balance of commercial, office, and public
• Design: intersections per square mile
• Destination Accessibility: jobs within 1 mile • Destination Accessibility: jobs within a 30 min by transit
• Distance to Transit: rail station, bus stops within ¼ mile
• Development Scale: MXD population and employment
• Demographics: household size, vehicle ownership
* Internal travel and walking, transit use, trip length
7D Factors Correlated with Reduced Travel
28 Nationwide Validation Sites
• 7 Florida sites (including ITE Trip Generation Handbook)
• 15 California sites
• 2 sites in Texas •
• 2 in Georgia, S Carolina
• 2 sites in Utah
• Variety of scale, mix, design
Atlantic Station, Atlanta Uptown District, San Diego
Irvine California Plano Texas
Mixed-Use Centers, California and Florida
Celebration Florida Otay Ranch California
South Davis, CA
South Davis, California
Moraga, CA
Mockingbird Station, Dallas Bay Street, Emeryville, CA
MXD Model Validation
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Exte
rnal
Ve
hic
le T
rip
s (1
00
0s)
Gross Trips Net Trips MXD Model Observed
Comparison of MXD Model to Other Methods (28 Validation Sites)
MXD Model Compared with ITE
Daily Predicted vs. Observed MXD External Vehicle Trips
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Predicted Trips (1000s)
Ob
serv
ed
Tri
ps
(10
00
s)
ITE MXD
MXD Acceptance
From Analytics to Tools
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S… S… S… S… S… S… S… S… S… S… S… S… S… S…
MXD BMP DRM ASAP
Capturing the Transportation
Benefits of Mixed Use Development
APA National Planning Conference
April 2012
Jerry Walters ◊ Fehr & Peers
ET+
Metropolitan Research Center – University of Utah
Fregonese Associates
Envision Utah
Salt Lake County
Wasatch Front Regional Council
Apps (requiring travel inputs in green)
Predictive Growth Model
Building and Land Use Types
Building Energy Consumption
7D Transportation Impacts
Return of Investment
H + T Costs
Air Quality and Climate Impacts
Fiscal Impact
Public Health
Employment Growth
Employment Resilience
Development Capital
Redevelopment Timing
Water Consumption
Transportation Safety
Workforce Housing
LEED-ND Application
Public Assets
Apps (requiring travel inputs in green)
7D App
Through pioneering research, University of Utah faculty have
modeled the effects of density (built space per acre), diversity
(land-use mix), distance to transit, destination accessibility, land-
use connectivity through design, development scale, and
demographics – the 7Ds, on internal capture of trips within mixed-
use developments (MXDs); external trips by walking, transit, and
private vehicle; and vehicle miles traveled (VMT).
ET+ will be expanded to include all trips and will develop interactive
coefficients to calculate internal capture, walk, transit, and private
vehicle trips, and VMT for comparison to current conditions and
future scenarios advancing 7D interactions.
7D Analysis - Innovations
• Pooled household travel data for MXDs in six
diverse regions
• Identified 239 MXDs through a bottom-up survey
process
• Included internal capture, mode choice for
external trips, and trip length as travel
outcome measures
Additional Innovations
• Estimated large number of 7D variables
consistently across regions
• Modeled travel relationships hierarchically
• Validated results through comparison to traffic
generation counts at an independent set of
mixed use sites in various parts of the U.S.
Six Diverse Regions
• Atlanta
• Boston
• Houston
• Portland
• Sacramento
• Seattle
Provide XY coordinates for trip ends, so we could zero in on individual sites when studying travel patterns to, from, and within MXDs
Provide individual parcel data, so we could study land-use mix down to the parcel level
Regions Based on Data Availability
Top-Down GIS-Based Approach
vs.
Bottom-Up Expert-Based Approach
Identifying MXDs
…A mixed-use development or district
consists of two or more land uses between
which trips can be made using local streets,
without having to use major streets. The
uses may include residential, retail, office,
and/or entertainment. There may be walk
trips between the uses.
New MXD Definition
Internal capture = 36%
Walking – 14%
Transit – 9%
Auto Trips – 7.7 miles
Example – RiverPlace (Portland)
239 MXDs
Metro
Survey
Year
MXDs
Mean Acreage
per MXD
Total Trip
Ends
Mean Trip
Ends per
MXD
Atlanta 2001 24 287 6,167 257
Boston 1991 59 175 3,578 61
Houston 1995 34 401 1,584 47
Portland 1994 53 116 6,146 116
Sacramento 2000 25 179 2,487 99
Seattle 1999 44 207 15,915 362
Total 239 211 35,877 150
Multiple Outcome Measures
INTERNAL – Dummy variable indicating that the trip remained within the development
WALK – Dummy variable indicating that the travel mode on a trip is walking (1=walk mode, 0=other)
TRANSIT - Dummy variable indicating that the travel mode on a trip is public bus or rail (1=transit, 0=other)
TDIST - Network trip distance between origin and destination locations for an external private vehicle trip, in miles
7D variables consistently defined
Density
Diversity
Design
Destination Accessibility
Distance to Transit
Development Scale
Demographics
Individual Level Variables
HHSIZE – Number of members of the
household
VEHCAP – Number of motorized vehicles
per person in the household
BUSSTOP – Dummy variable indicating that
the household lives within ¼ mile of a
bus stop (1=yes, 0=no)
ACTDEN – Population + employment density per square mile
JOBPOP – Balance of jobs to population within the MXD
LANDMIX – Entropy index that captures the variety of land uses based on acreage
INTDEN - Number of intersections within the MXD per square mile of gross area
EMPMILE – Total employment within one mile of the traffic analysis zones intersecting the MXD
EMP30T – Total employment within 30 minutes by transit of traffic analysis zones intersecting the MXD
STOPDEN – Number of bus stops within the MXD per square mile of gross area
RAIL – Rail station located within the MXD (1 = yes, 0=no)
MXD Level Variables
Region Level Variables
REGPOP – Population within the region
REGEMP – Employment within the region
REGACT – Activity within the region
(population + employment)
SPRAWL – Measure of overall regional
sprawl from same source
Hierarchical Modeling
Level 1 Trips/Individuals/Households
Level 2 MXDs
Level 3 Regions
Log odds of internal capture
(log-log form)
Home-Based Work Home-Based Other Non-Home Based
Coeff t-ratio p-value Coeff t-ratio p-value Coeff t-ratio p-value
constant -1.75 -2.43 -5.72
EMP 0.208 3.28 0.002
AREA 0.486 3.61 0.001 0.468 4.58 <0.001
JOBPOP 0.389 2.62 0.010 0.399 4.55 <0.001
INTDEN 0.385 1.92 0.055 0.638 4.95 <0.001
HHSIZE -1.33 -6.03 <0.001 -0.867 -13.0 <0.001 -0.237 -4.54 <0.001
VEHCAP -0.990 -4.15 <0.001 -0.590 -8.19 <0.001 -0.163 -3.00 0.003
pseudo-R2 0.01 0.20 0.30
Log odds of walking on external
trips (log-log form)
Home-Based Work Home-Based Other Non-Home Based
Coeff t-ratio p-value Coeff t-ratio p-value Coeff t-ratio p-value
constant -5.55 -10.96 -15.09
AREA -0.415 -4.27 <0.001
ACTDEN 0.370 2.74 0.007 0.377 3.12 0.003
JOBPOP 0.226 2.46 0.015 0.219 3.83 <0.001
INTDEN 0.803 5.05 <0.001
EMPMILE 0.385 3.12 0.002 0.450 5.05 <0.001 0.440 5.09 <0.001
HHSIZE -1.57 -6.29 <0.001 -0.486 -5.05 <0.001 -0.281 -2.59 0.010
VEHCAP -1.84 -7.00 <0.001 -0.768 -7.62 <0.001 -0.242 -2.13 0.033
pseudo-R2 0.19 0.51 0.64
Log odds of using transit on external
trips (log-log form)
Home-Based Work Home-Based Other Non-Home Based
Coeff t-ratio p-value Coeff t-ratio p-value Coeff t-ratio p-value
constant -4.32 -6.08 -2.69
ACTDEN 0.324 2.89 0.005
INTDEN 1.12 4.44 <0.001
EMP30T 0.209 2.98 0.004 0.134 3.29 0.002
HHSIZE -1.14 -6.31 <0.001 -0.958 -8.48 <0.001
VEHCAP -1.68 -8.56 <0.001 -1.09 -8.24 <0.001 -0.340 -3.74 <0.001
BUSSTOP 0.357 2.08 0.037 0.467 4.04 <0.001
pseudo-R2 0.47 NA NA
Distance of external automobile trips
(semi-log form)
Home-Based Work Home-Based Other Non-Home Based
Coeff t-ratio p-value Coeff t-ratio p-value Coeff t-ratio p-value
constant 6.54 4.33 8.99
AREA 1.07 2.92 0.004
JOBPOP -0.298 -1.88 0.061 -0.356 -2.38 0.018 -0.282 -2.05 0.041
INTDEN -0.832 -2.06 0.041
EMP20A -0.697 -4.79 <0.001 -0.823 -5.69 <0.001
EMP30A -1.19 -6.05 <0.001
HHSIZE 2.76 8.08 <0.001 0.772 5.06 <0.001 0.520 2.58 0.010
VEHCAP 2.76 7.26 <0.001 1.48 9.22 <0.001 1.06 5.12 <0.001
pseudo-R2 0.11 0.03 0.05
Primary Determinants of
Reduction in External Auto Trips
• The total and the relative amounts of population and
employment on the site
• The site size and activity density
• The amount of employment within walking distance of the site
• The pedestrian-friendliness of the site (small block size)
• The access to employment within a 30 minute transit ride of the
site.
• The size of households and their auto ownership
Variety of scale, mix, design
• 15 California sites
• 7 Florida sites (including ITE Trip Generation Handbook)
• 2 Texas sites
• 2 Utah sites
• 1 Georgia site
• 1 North Carolina site
28 NATIONWIDE VALIDATION SITES
Atlantic Station, Atlanta Uptown District, San Diego
Irvine, California Plano, Texas
Mixed-Use Centers, California and Florida
Celebration, Florida Otay Ranch, California
SOUTH DAVIS, CA
MORAGA, CA
Mockingbird Station, Dallas Bay Street, Emeryville, CA
MXD MODEL VALIDATION VS. COUNTED SITES
MXD MODEL COMPARED WITH ITE
ITE
MXD
Model Validation
UTAH VALIDATION CASE STUDIES
• Visited seven sites – Selected two sites
• Final sites chosen based on:
Sufficient mix of land uses
Feasibility of count data collection
SITE SELECTION – COUNTED SITES
Redstone Summit County
• 52 Acres
• 32,000 sf Office
• 20,000 sf Medical Office
• 210,000 sf Retail
• 8 Screen Movie Theater
• 320 Townhouse Units
Quarry Bend Sandy
• 100 Acres
• 450,000 sf Retail (includes Wal-
• 120 Apartment Units
• 275 Townhouse Units
• City Park
DESCRIPTION OF TWO SITES
REDSTONE
QUARRY BEND
11,000
11,500
12,000
12,500
13,000
13,500
14,000
14,500
15,000
ITE
ITE w/ Internal Capture
MXD Counts
Dai
ly V
ehic
le T
rip
s External Daily Vehicle Trips Comparison
Redstone
15% Reduction
DAILY TRIP COMPARISON
18,500
19,000
19,500
20,000
20,500
21,000
21,500
22,000
22,500
23,000
ITE
ITE w/ Internal Capture
MXD Counts
Daily V
ehic
le T
rips
External Daily Vehicle Trips Comparison
Quarry Bend
12% Reduction
DAILY TRIP COMPARISON
Extension of 7D Analysis to Austin,
Minneapolis, and Salt Lake Regions
Include All Trips from All Regions in Final
Modeling Exercise
Analyze All Catalytic Sites
New Tasks
There is a Better Way to Grow…
The Wasatch Choice
for 2040:
Regional Vision for
Land Use and
Transportation
There is a Better Way to Grow…
Focus growth in town centers, linked together with modern, efficient transportation systems.
Catalytic Sites
Provo Site
Key Downtown characteristics for 2040 growth
Downtown Provo Positioned to be Regional Economic and Cultural Center
Extension of 7D Analysis to Austin,
Minneapolis, and Salt Lake Regions
Include All Trips from All Regions in Final
Modeling Exercise
New Tasks
