What is the Travel Demand Model?
VLMPO CAC-TAC Joint Meeting
April 23, 2014
Why are we here?
• Assumption: Land use policy decisions
impact transportation infrastructure
(investment and costs)
• Demonstrate how the VLMPO-JLUS 2035
Travel Demand Model can be used to
show impacts on transportation
infrastructure based on land use policy
• What is the Model?
• How does the Model Work?
• How is the Model used in Transportation?
• How is the Model used in Land-Use
• What will Local Officials Learn about Land-
use and transportation policy from the
What is the Model?
The Travel Demand Model is a tool (one of
many) that can be used to provide more
information to decision makers on
The TDM should not be used as the final
determining factor in any decision, it should
be one of many resources and inputs
What is the Model?
• The model is the data, not the software
– Traffic Analysis Zones (TAZs)
– Road Networks
– Socioeconmic Data (tabulated at TAZ level)
• School Enrollment (school location)
• Retail Employment
• Wholesale Employment
• Service Employment
• Manufacturing Employment
• Lots of Regional and National Defaults (can be changed)
1. Trip Generation
– Number and Type of Trips Each TAZ Produces or Attracts is
2. Trip Distribution
– Trips are Distributed by TAZ from Origins to Destinations
3. Mode Split
– Assigns Trips to Cars, Public Transit, Biking, Walking, etc.
– Not Used in VLMPO TDM, Alternative Modes not Large
4. Trip Assignment
– Trips are Assigned to Highway Network, Using Shortest Path
– Once Roadway Becomes Congested, Next Shortest Path is
What does it mean?
• Roads are assigned a Level of Service (A
thru F) Grading Scale
– A=Good, Free Flowing Traffic at Peak Travel
– F=Very Bad, Standstill Traffic at Peak Travel Time
• Planners and Engineers then develop
transportation projects to ease congestion on
links where Level of Service is improved
• Exit 2 Lake Park Bellville Road
• Oak St/Woodrow Wilson Area
• Bemiss Rd and Forest Street Corridors
1. Land Use Inputs for Forrest St.
2. 2035 No Build – 2 lane, other inputs
3. 2035 Build – 5 lane, with school, Park 3
4. 2035 – 4 lane, w/o school, Park 3 lane
5. 2035 – 5 lane, w/o school, Park 3 lane
• Can be changed at any time, most all
assumptions can be tweaked to answer
the questions of local officials
• Is macro, not parcel specific