Economic and behavioral effects
of transportation infrastructure
Testimony to the New Jersey Clean Air Council
April 14, 2010
Robert B. Noland
Professor, Rutgers University, Bloustein School of
Planning and Public Policy
Director, Alan M. Voorhees Transportation Center
Major issues
• How does funding of transportation
infrastructure affect air quality and greenhouse
gas emissions?
• How do people respond to changes in
transportation infrastructure?
• What are the effects of transportation
infrastructure on economic productivity and
development?
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Transportation funding objectives
• Reduce congestion
• Increase economic development
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Do expanded roads reduce
congestion?
• When the cost of travel is reduced, economic
theory suggests that…
– Travelers choose to move to their preferred travel
time and route – peak congestion stays the same
– New trips not previously taken are generated
– Longer trips are made
– People use their car instead of public transit
– New land is opened to development, leading to
more and longer car trips
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Elastic Demand & Supply
S1: Supply before
S2: Supply after
P1
P3
P2
D3: Exogenous Demand growth
D1: Demand before
Q1
Q2 Q3
Quantity of Travel (VMT)
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Empirical studies confirm theory
• A wide range of empirical research studies confirm that
new roads spur increased car travel
• But are roads built because planners foresee demand?
– Research evidence suggests that expanded roads cause
growth in car travel
• In the long run, new and expanded roads will not
reduce congestion
– Transportation models do not fully capture these effects
Noland, R.B. & Lem, L.L. 2002, "A review of the evidence for induced travel and changes in transportation and environmental
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policy in the US and the UK", Transportation Research Part D, vol. 7, no. 1, pp. 1-26.
What about vehicle emissions?
• Improving traffic flow can reduce emissions
from cars
• But this effect does not last
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Break-even point for NOx
Induced trips-mix
Induced trips-all coldstarts
Emissions of NOx (Kg)
130
120
Initial level of emissions
110
96.6 kg
100
90
After adding lane
80
70
60
50
4800
14% more cars
11.5% more cars
5702
5575
5000
5200
5400
5600
5800
Traffic Flow (veh/h)
Noland, R.B. & Quddus, M.A. 2006, "Flow improvements and vehicle emissions: Effects of trip generation and emission control
technology", Transportation Research Part D, vol. 11, no. 1, pp. 1-14
6000
There are benefits to more traffic
• Allows more people to travel when and where
they want
– This increased mobility increases consumer
welfare
– However, identifying the benefits depends on the
evaluation method used
– Methods used by transportation planners tend
not to capture the long-term distributional effects
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Distribution of Benefits from Accessibility
Increases
Cost of land
Before
capacity
addition
Land
prices
after
increase
in
available
supply
Initial land
price
response
Travel time
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What are long run costs and benefits?
• Benefits
– Allows more land to be developed, benefiting
those who own land that is now more accessible
– Can allow an increase in supply of housing and
commercial development, lowering costs to
consumers
• Costs
– Developments are more car-dependent and thus
emissions increase
– Environmental costs associated with sprawl
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Can transportation funding and policy
support environmental goals?
• Change incentive structure
– Funding of roads versus public transit
– Change mix of user fees for both roads and public
transit
• Development patterns make a difference
– Focus new development on areas that are transit
accessible
– This can provide options for people to avoid using
motor vehicles
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