How to Troubleshoot Apps for the Modern Connected Worker
Analyzing Travel Demand Management Strategies: the Promise of Activity-Based Travel Demand Models
1. Analyzing Travel Demand
Management Strategies: the Promise of Activity-
Based Travel Demand Models
Elizabeth A. Sall
SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY
Transportation Research Board Annual Meeting
Sunday January 13th, 2013
2. Overview of Questions I Hope to Answer
1. What is an “Activity-Based Travel Demand Model”?
2. What is it about these activity models make them
better (or not) for analyzing TDM Strategies?
3. What does a specific TDM strategy look like in an
activity model? (a few examples)
4. Who has these activity models anyways?
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3. Activity-Based Travel Demand Model?
A few principles
• People want to do activities, and they travel in order
to participate in them travel is a derived demand.
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4. Activity-Based Travel Demand Model?
A few principles
• Household and social structures influence activity
and travel there‟s a lot more to „you‟ than the zone
around you.
Flickr: MNicoleM
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5. Activity-Based Travel Demand Model?
A few principles
• No cart before the horse / driving home if you
walked to work / leaving work before you got there
interdependence explicitly recognized.
If it looks like But you don’t
this outside have a car at
every morning… work now…
then you’ll So even if
probably the evening auto
decide to… commute is cake,
you’ll need to…
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6. Activity-Based Travel Demand Model?
A few principles
• No cart before the horse driving home if you walked
to work / leaving work before you got there
interdependence explicitly recognized.
If this area where you You realize that if
work has a congestion you drive like this
fee from 4 to 6 pm… In the AM…
That it will cost
you like this $
In the PM…
And you live here…
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7. Activity-Based Travel Demand Model?
A few principles
Sum of all small behavior types is the majority of
behavior we are all unique, and that is important.
0.18
0.16
0.14 Income $0-30k
P robability Dens ity
Income $30-60k
0.12 Income $60-100k
0.1 Income $100k+
0.08
0.06
0.04
0.02
0
$- $5 $10 $15 $20 $25 $30
Value of T ime ($/Hour)
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8. Activity-Based Travel Demand Model?
What it comes down to:
• A less-cool-looking version of sim-city.
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9. Activity-Based Travel Demand Model?
Every Sim has a:
• role
• income
• age
• gender
• household
Population Synthesis
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10. Activity-Based Travel Demand Model?
Every Worker Sim
chooses a workplace
based on:
• Job type/income
match
• Accessibility to work
Workplace Destination Choice
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11. Activity-Based Travel Demand Model?
Every Sim Household
decides how many cars
they want:
• How easy is it to get to
work with and without
a car?
• How easy is it to get to
other stuff around the
house with and
without a car?
• Demographics
Auto Availability
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12. Activity-Based Travel Demand Model?
Every morning, each Sim
wakes up and asks
themselves “Gee, what
am I going to do today?”
• How easy is it to get to
work?
• What else do I need to
do today?
• Demographics
Tour Generation
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13. Activity-Based Travel Demand Model?
If they are going
somewhere other than to
work, the Sim will pick
what the primary reason
for leaving the house is:
• Accessibility
• Schedule
Tour Destination Choice
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14. Activity-Based Travel Demand Model?
Then they need to pick
the primary way that they
are going to get there.
• Accessibility by mode
Tour Mode Choice
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15. Activity-Based Travel Demand Model?
If they need to make
stops along the way, they
pick places that are
convenient to the tour
mode that they have
chosen to their primary
destination.
• How far a detour is it
from my main trip?
• Near transit transfer
point/freeway exit?
Intermediate Stop Choice
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16. Activity-Based Travel Demand Model?
Once the entire tour is
planned out, the Sim
choses the exact mode
that they will use for each
sub-part of their
excursion from home
(aka tour).
Trip Mode Choice
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17. Activity-Based Travel Demand Model?
Based on congestion
levels and other
preferences, the Sim then
navigates their way
through the network to
participate in activities
and carry out their plans.
Route Choice
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18. Activity-Based Travel Demand Model?
All of these choices are
carried out by the
individual with full
knowledge of their:
• Other choices
• Activity needs /
Household
• Physical / Temporal
constraints
• Demographics
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19. Good for TDM Strategy Analysis?
• Depends on the strategy. Can it be represented in
ABM framework? Can it be just as well represented
in 4S model?
• Existing Tools? Do you already have an AB model?
• Got Data? Does the data already give you the answer
to the question that you have?
• Risk/Reward? Depends on the questions that you
need to have answered and how sure you want to be
about them.
(And if you can‟t articulate a question that you are trying to answer, there are much more
rewarding places to sink time and money)
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20. ABM -- Good for TDM Strategy Analysis?
Pros
• Understands induced and latent demand
If you build that HOT lane, more people are going to
drive.
If you make it easier to park, more people are going
to drive.
Hard to build your way out of congestion.
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21. ABM -- Good for TDM Strategy Analysis?
Pros
• Explicit representation of interdependencies
If my child has swim practice, I need to drive today.
If I need to stay late at work and transit is bad after
rush hour, I will drive.
If I bike down a hill, I have to bike back up it.
Bike Accessibility To Bike Accessibility From
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22. ABM -- Good for TDM Strategy Analysis?
Pros
• Lots of choices for performance measures
Each sim is tracked and can be accounted for
individually or across multiple demographic or
geographic dimensions.
Future GHG Production per HH
sfmobility.org
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23. ABM -- Good for TDM Strategy Analysis?
Pros
• Simulation framework is flexible
You can “do something else” to your Sim
Your Sim can become aware of new information
Your Sim‟s decisionmaking can have
more/new/better rules or models
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24. ABM -- Good for TDM Strategy Analysis?
Pros
• Simulation framework is flexible
Our Sims just learned about the benefits of bike lanes
Trip Difference - Bike Projects
Daily Tours v4.1 Harold v4.3 Fury
Bike 500 0.1% 3,000 0.8%
Walk 1,100 0.0% -500 -0.0%
Transit 850 0.0% -600 -0.0%
Auto -2,400 -0.0% -1,300 -0.0%
Total 0 0.0% 600 0.0%
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25. ABM -- Good for TDM Strategy Analysis?
Pros
• Can easily implement what if scenarios:
Can still do sans data. Test a hypothesis!
What if we had a compressed work week?
We could assume that:
commuting would be 20% less
work duration a few hours longer
only full time workers affected
Tested in Burlington:
-4% overall trips
Only slight VMT decrease
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26. ABM -- Good for TDM Strategy Analysis?
- Pros
• Understand the system
• Recognize unintended consequences
Can we build our way out of GHG issues with bike
lanes?
If our transit system becomes the most popular thing
on earth how many people would ride it?
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27. ABM -- Good for TDM Strategy Analysis?
Cons
• Is it overkill ?
• Is it easier to run a pilot and find out vs. spend a few
years and $1 million developing a model ?
• Do you really just need a back of the envelope guess?
….but once you have it you will find so many questions
that it is good at answering.
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28. Who has these tools?
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29. Thanks for inviting me
to this community to speak!
(we are open to suggestions about how to
provide info for better decisions)
elizabeth@sfcta.org
www.sfcta.org/modeling
SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY
30. “…A major advantage of activity based modeling lies in
its ability to give a better understanding and prediction
of traveler responses to TDM measures and other
types of transportation policies. “
“ These improved estimates of the changes in important
transportation variables, then, provide the basis for the
development of more accurate estimates of emission
reductions that would result from the implementation
of one or more TDM strategies.”
Shiftan Y. et al “Activity-based Modeling as a Tool for Better
Understanding Travel Behaviour” IATBR Conference
Paper. Lucern, 10-15 August 2003.
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31. “…trip based four step aggregate methodology, is
inadequate in analyzing the sustainable transport
policies. “
“A review of … activity based travel demand modeling
found that they are capable of handling such policies
better than conventional models and are assistive to
the decision makers in arriving at right mix of polices
specific to the situations. ”
Malayath, Manoj and Ashish Verma. “Activity based travel
demand models as a tool for evaluating sustainable
transportation policies” Research in Transportation
Economics Volume 38/Issue 1. Feb 2013.
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Notas do Editor
…but I might not answer them in order!
Cat Telecommute photo: License Some rights reserved by seandreilingerI’m sure Academics and practitioners alike can argue with this list, but I think these are important for our discussion today.Travel is a derived demand. This is an important consideration especially if we are thinking about serving people’s needs with less of it. However (unrelated), it’s also important to consider that just as there is a concept of a “travel budget” for a day (a ceiling amount of traveling you are willing to do), there is also a psychology concept of a “social interaction floor” – the fact that people who aren’t going to work often partake in many more out of home activities…they go to the grocery store much more frequently, etc.This is an important consideration when devising TDM strategies such as telecommuting. We see it in the data, and we can also actually also show it with an AB model.Telecommuting can mean different things in different places – and that can mean different things for the efficacy of using it as a TDM strategy.Person on the left is being social with his cat…and looking out the window at suburbia – he’ll probably make a few trips (probably driving) out of the house just to interact with real people.People on the right walked down the street to a coffee shop.A good AB model understands that there isn’t just substitution effects for in- and out-of home activity…but that there is latent demand for out of home activity.
A lot of models or sketch planning tools tend to aggregate together demographics from what is around you into “you”. AB modeling explicitly recognizes that these sums of people actually exist in a structure…and that structure matters. Households with school-age children behave extremely differently than households without children. A parent that needs to drive their kid to school at a certain time is far less like to flex their time at work to take advantage of off-peak commuting hours…and is also a lot less likely to vanpool/carpool to work. Most newer activity-based models explicitly understand how a kid’s school location and transportation options directly impact their parent’s day-patterns.Even older activity-based models contain variables and understandings of how your household structure affects your choices.