Analyzing Changes to Truck Size and Weight Regulations
Methods for States
presented to
AASHTO Subcommittee on Highway Transport
presented by
Donald Ludlow, Cambridge Systematics
June 28, 2011
How to analyze TSW proposals
Weaknesses of past studies: TRB Special Report 267
» The methods used in past studies have not produced satisfactory
estimates of the effect of changes in truck weights on bridge costs.
» It is not possible to predict the outcomes of regulatory changes with
high confidence.
» It is essential to examine the safety consequences of size and weight
regulation. Research and Monitoring needed to understand the
relationship of truck characteristics and truck regulations to safety
and other highway costs are not being conducted today.
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How to analyze TSW proposals:
AASHTO Evaluation Criteria
Safety—Will the proposal improve safety on the interstate?
Economic Benefit—Will the proposal produce a positive economic outcome?
Infrastructure preservation, renewal, and capacity—Will the proposal adversely affect
the condition and/or the performance of highway infrastructure?
Congestion reduction—Will the proposal reduce highway congestion?
Modal diversion—Will the proposal cause a shift of traffic to highway from rail or
waterways that will have adverse impacts on infrastructure, safety or the environment?
Financing assurance—Will the proposal provide guaranteed funding to equal the costs of
necessary infrastructure improvements and increased enforcement?
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VMT Shift*
VMT Pre-test / Post-test
» How many trucks before the change?
» How many trucks after the change?
VMT shift by type of truck
»
»
»
FHWA Classifications
State-specific configurations
Develop controlling assumptions
– Shipper / carrier outreach
– Commodity / economic analysis
VMT shift by functional classification
»
»
Shift from local to Interstate
Develop controlling assumptions
– Shipper / carrier outreach
Tools / Data
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»
»
»
Vehicle Travel Information System (VTRIS)
Vehicle classification counts (state)
WIM
*Method applies to “pioneering” states
In the future, we may have REAL
observations from which we can derive
more accurate factors
How to analyze TSW proposals:
AASHTO Evaluation Criteria
Safety—Will the proposal improve safety on the interstate?
Economic Benefit—Will the proposal produce a positive economic outcome?
Infrastructure preservation, renewal, and capacity—Will the proposal adversely affect
the condition and/or the performance of highway infrastructure?
Congestion reduction—Will the proposal reduce highway congestion?
Modal diversion—Will the proposal cause a shift of traffic to highway from rail or
waterways that will have adverse impacts on infrastructure, safety or the environment?
Financing assurance—Will the proposal provide guaranteed funding to equal the costs of
necessary infrastructure improvements and increased enforcement?
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How to analyze TSW proposals: Safety
Are the heavier trucks safe to operate?
» Driver training
» Equipment certification
» Vehicle dynamics
What is the accident rate by truck?
» By functional classification
» From research
» From observation
Apply shifts in VMT by truck configuration against crash rates
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How to analyze TSW proposals:
Infrastructure preservation, renewal, capacity
Bridges
» Test bridges for strength – will the bridges accommodate the heavier
trucks?
» Test bridges for fatigue – how will the trucks affect bridge life (structure
and deck)
» How do results affect life cycle costs?
Pavements
» Test pavements for fatigue (e.g. DARWIN ME)
» How do results affect life cycle costs?
Capacity / Congestion
» Analyze VMT shift using state travel demand models
» Use HERS-ST (passenger car equivalents) for urban areas if there is no
model available
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How to analyze TSW proposals:
Modal Diversion
Rail-to-truck diversion
» Will loads shift from rail to truck?
» Which commodities are vulnerable?
» What other factors influence the shift?
Conduct outreach
» Shipper interviews
» Railroad outreach
Conduct data analysis
» Develop controlling assumptions
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–
–
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Commodities
Distances
Origin-destination pairs
Ton-mile costs
» Estimate candidate loads
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How to analyze TSW proposals:
Financing Assurance
Will the proposal provide guaranteed funding to equal the costs of necessary
infrastructure improvements and increased enforcement?
Estimate costs (or savings) of infrastructure improvements
Estimate costs of increased enforcement
Estimate costs of increased permit administration
Estimate increased permit revenue
Other costs / savings
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How to analyze TSW proposals
Route Selection—Routes suitable for increased size and/or weight on the interstate will be
determined by the state based on the evaluation criteria above and the conditions below.
Infrastructure Assessment—No interstate route (including access) will be approved for
increased size and weight before an assessment determines that it can be done without
serious adverse impacts on highway infrastructure (including access) or before necessary
improvements are made.
Cost Estimate—A cost estimate must be carried out to determine the total cost and timing
of investments made necessary by the change in truck size and weight.
Safety Requirements—Vehicles operating under the increased size and weight limits will be
required to be of the highest available quality, including all of the standard safety
technology; drivers will be required to have outstanding safety records; and the companies
will be required to have strong safety histories.
Monitoring and reporting—A rigorous monitoring system must be established to produce
regular reports to determine whether the outcome of the change in federal truck size and
weight limits on the interstate are consistent with the evaluation criteria.
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How to analyze TSW proposals (con’t)
Monitoring and reporting—A rigorous monitoring system must be established to produce
regular reports to determine whether the outcome of the change in federal truck size and
weight limits on the interstate are consistent with the evaluation criteria.
Infrastructure funding—A mechanism must be in place that will guarantee that the cost of
any improvements determined to be necessary by the Infrastructure Assessment will be
met by revenues from the benefiting carriers and shippers.
Implementation funding—The federal government must provide the funds necessary for
enforcement, monitoring and administration necessary for the state DOTs to implement the
changes in truck size and weight on the Interstate system.
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Questions and Discussion
Thank You!
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