Fwd: to 2020 Planners: Widening roads induces traffic. Studie

[Ken Medlin <dev-plan@moscow.com>]

Subject:     to 2020 Planners:  Widening roads induces traffic.  Studies
Sent:        3/19/20 7:35 AM
Received:    3/16/00 8:11 AM
From:        DPlum65@aol.com
To:          smartgrowth@onenw.org  [ Forward To:  Moscow Community Vision Advocates:  These references come too late for our constituencies to change the directions that US-95 are now set to move in, but they may be useful as educational material -- in hindsight -- for reflecting on any future transportation planning and decision-making. As usual, those in authority have long since decided way ahead of public disclosures the character of our state, regional and local traffic patterns over the next quarter century. As I havae suggested many times on this list, without citizen education and organization, communities are at the mercy of politicians at the upper echelons of power. From 4-wheelers to 22 wheelers, let 'em roll!  "And that's the way it is."  Ken M.]

=====  A message from the 'smartgro' discussion list  =====

Here are several studies from the Sierra Club archives on induced 
traffic/widening roads.  It appears that if the 2020 Plan widens 22 roads and 
builds several new ones, that this is not the right path to achieve 25% 
alternative transportation, nor to meet clean air regs to achieve future 
transportation funding.
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Induced
Traffic
Confirmed 
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The jury is in! Recent studies show that building or widening highways 
induces more traffic, called induced travel. Shortly after the lanes or road 
is opened traffic will increase to 10 to 50% of the new roadway capacity as 
public transit or carpool riders switch to driving, or motorists decide to 
take more or longer trips or switch routes. This is short-term induced 
travel. In the longer term (three years or more), as the new roadway capacity 
stimulates more sprawl and motorists move farther from work and shopping, the 
total induced travel rises to 50 to 100% of the roadwayıs new capacity. This 
extra traffic clogs local streets at both ends of the highway travel. The 
following table summarizes these studies.

Elasticity -- % new capacity filled with induced traffic   Short-term 
Long-term (3+ years) 
SACTRA   50 - 100% 
Goodwin  28% 57% 
Johnson and Ceerla    60 - 90% 
Hansen and Huang   90% 
Fulton, et al. 10 - 40% 50 - 80% 
Marshall   76 - 85% 
Nolan  20 - 50% 70 - 100% 

Fulton, Lewis, Daniel Meszler, Robert Noland and John Thomas. "A Statistical 
Analysis of Induced Travel Effects in the U.S. Mid-Atlantic Region," 
presented at Transportation Research Board, Washington, DC. Jan. 2000.

Goodwin, Phil. "Empirical Evidence on Induced Traffic," Transportation, Vol. 
23, No. 1, Feb. 1996, 35-54.

Hansen, Mark and Yranling Huang. "Road Supply and Traffic in California Urban 
Areas," Transportation Research A, 31. 205-218. 1997.

Johnston, Robert and Raju Ceerla. "The Effects of New High-Occupancy Vehicle 
Lanes on Travel and Emissions," Transportation Research, Vol. 30A, No. 1, 
35-50. 1996.

Marshall, Norman. "Evidence of Induced Demand in the Texas Transportation 
Instituteıs Urban Roadway Congestion Study Data Set," presented at 
Transportation Research Board, Washington, DC. Jan. 2000.

Standing Advisory Committee on Trunk Road Assessment, Department of Transport 
(UK). Trunk Roads and Generation of Traffic. HMSO, London. 1994.

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William K. Medlin
Dev-plan associates
930 Kenneth Street
Moscow ID 83843
208/892-0148
dev-plan@moscow.com