Highway Infrastructure: FHWA's Model for Estimating Highway Needs Has
Been Modified for State-Level Planning (Letter Report, 02/14/2001,
GAO/GAO-01-299).
The Federal Highway Administration (FHWA) developed the state-level
version of the Highway Economic Requirements System (HERS-ST) model as
an investment-analysis tool for highway planning at the state level.
FHWA officials believe that some state departments of transportation
will find the analysis that the HERS-ST model produces useful because it
demonstrates the potential results of highway investment decisions from
an economic point of view. FHWA is conducting a pilot project for its
prototype HERS-ST model with those states that volunteered to test the
model. FHWA distributed to these states HERS-ST software, technical
manuals, and sets of state highway data with which to run the model.
FHWA then provided an overall orientation and technical training and
addressed states' questions during a workshop. Officials from a sample
of the states planning to participate reported that they are primarily
interested in taking advantage of the model's use of benefit-cost
analysis to assess alternative highway improvements. If the pilot
project shows that states view the HERS-ST model as a useful tool, FHWA
expects to upgrade the model for future users. In doing so, it would
consider both enhancements that have already been planned for the
national-level HERS model and changes targeted specifically to HERS-ST.
Changes specifically to improve the HERS-ST model's usefulness to states
include converting the model to a menu-driven system to improve its ease
of use or revising the model's data input format so that it matches
FHWA's current state highway data reporting requirements.
--------------------------- Indexing Terms -----------------------------
REPORTNUM: GAO-01-299
TITLE: Highway Infrastructure: FHWA's Model for Estimating
Highway Needs Has Been Modified for State-Level Planning
DATE: 02/14/2001
SUBJECT: Highway planning
Highway research
Public roads or highways
Federal/state relations
Management information systems
Computer modeling
Federal aid for highways
Economic analysis
Cost effectiveness analysis
IDENTIFIER: DOT Highway Economic Requirements System
Oregon
Indiana
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GAO-01-299
A
Report to Congressional Committees
February 2001 HIGHWAY INFRASTRUCTURE
FHWA's Model for Estimating Highway Needs Has Been Modified for State- Level
Planning
GAO- 01- 299
Letter 3 Appendixes Appendix I: Scope and Methodology 22
Appendix II: Information About HERS Models 24 Appendix III: Questionnaire
for States That Asked to Participate
in FHWA's Pilot Program for the State HERS Model 33 Appendix IV: GAO
Contacts and Staff Acknowledgments 37
Tabl es Table 1: HERS Pilot Project States and Eight States Randomly
Selected for Interviews 23
Table 2: Key Differences Between the HERS Model and State- Level HERS Models
31 Figures Figure 1: Simplified Representation of the HERS Modeling Process
7
Figure 2: States Participating in the HERS- ST Pilot Program 15
Abbreviations
DOT Department of Transportation FHWA Federal Highway Administration HERS
Highway Economic Requirements System HERS- ST state- level version of the
Highway Economic Requirements System
GAO U. S. General Accounting Office TEA- 21 Transportation Equity Act for
the 21st Century GIS geographic information system HPMS Highway Performance
Monitoring System MPO metropolitan planning organization EPA Environmental
Protection Agency HERS/ OR Oregon's version of the Highway Economic
Requirements System
HERS/ IN Indiana's version of the Highway Economic Requirements System
Lett er
February 14, 2001 The Honorable Bob Smith Chairman The Honorable Harry Reid
Ranking Member Committee on Environment
and Public Works United States Senate
The Honorable Don Young Chairman The Honorable James L. Oberstar Ranking
Democratic Member Committee on Transportation and Infrastructure
House of Representatives Federal and state governments have played a vital
role in the nation's economy by facilitating the movement of people and
goods through significant investments in highways. At the federal level, the
Department of Transportation's (DOT) Federal Highway Administration (FHWA)
uses a
computer model known as the Highway Economic Requirements System (HERS) to
estimate the future investment required to maintain and improve the nation's
highways. DOT reports the results of this analysis to the Congress on a
biennial basis. However, state governments make a large number of highway
infrastructure investment decisions. States currently use a variety of
analytic tools to make these decisions. Interest in using
HERS at the state level has grown. Two states- Indiana and Oregon- are
already using customized versions of the model, and in December 2000, FHWA
began a pilot project to test its state- level version of HERS, called HERS-
ST, with interested states.
The Transportation Equity Act for the 21st Century (TEA- 21) directed GAO to
evaluate and report to the Congress on the extent to which the HERS model
can be used to provide states with useful information for their planning
efforts. Accordingly, this report describes (1) why FHWA developed a state-
level HERS model, (2) how FHWA is making the statelevel
HERS model available to states, (3) how states expect to use the model, and
(4) how FHWA could improve the model, including improvements already planned
and additional changes that might increase the state- level HERS model's
usefulness, including the incorporation of additional data. To address these
issues, we built on our June 2000 report,
which focused on the federal HERS model, 1 by reviewing documentation for
the federal and state- level models and interviewing the models' developers
and managers. We interviewed FHWA officials about the HERSST
pilot project. In addition, to identify how states might use the HERS- ST
model, we first randomly selected 8 states from a list of 16 states that
initially volunteered to participate in FHWA's pilot project. For each of
the selected states, we asked state transportation officials to identify how
they plan to use the HERS- ST model and how, based on their current
understanding, the model might be improved. Finally, to draw on the
experiences that Indiana and Oregon have had with other state- level HERS
models, we interviewed transportation officials from these states about
changes that could be made to the HERS- ST model's assumptions and data to
improve the usefulness of the model. See appendix I for further information
on our scope and methodology.
Results in Brief FHWA developed the HERS- ST model as an investment-
analysis tool for highway planning at the state level. FHWA officials
believe that some state
departments of transportation will find the analysis that the HERS- ST model
produces useful because it demonstrates the potential results of highway
investment decisions from an economic point of view. These officials
recognized that the national- level HERS model's ability to compare the
benefits of alternative highway improvements to the related costs was an
improvement over previous highway planning models, which used engineering
standards to identify deficiencies and select improvements without regard to
their economic merit. They concluded that developing a
state- level HERS model might offer states a similarly useful analytical
tool. In addition, two states- Indiana and Oregon- recently started using
their
1 Highway Infrastructure: FHWA's Model for Estimating Highway Needs Is
Generally Reasonable, Despite Limitations (GAO/ RCED- 00- 133, June 5,
2000).
own customized versions of the national model. These states have already
found their models useful for determining future highway needs and planning
highway projects. After its positive experience with the nationallevel HERS
model and the model's successful adaptation in two states, FHWA began to
develop HERS- ST in 1999. FHWA expects that states will use the HERS- ST
model to facilitate planning for highway investment.
FHWA is conducting a pilot project for its prototype HERS- ST model with
those states that volunteered to test the model. Interest in the HERS- ST
model has been higher than FHWA officials first expected, with 20 states
volunteering to participate in the pilot project. In December 2000, FHWA
distributed to these states HERS- ST software, technical manuals, and sets
of state highway data with which to run the model. FHWA then provided an
overall orientation and technical training and addressed states' questions
during a February 2001 workshop. Following a test period, FHWA plans to
evaluate states' interest and success in using the model and report the
results in August 2001. On the basis of that evaluation, FHWA will make
decisions about whether or how to expand its support for the model and how
to improve it. Officials from a sample of eight of the states planning to
participate in the
HERS- ST pilot project reported that they are primarily interested in taking
advantage of the model's use of benefit- cost analysis to assess alternative
highway improvements. Though these officials had not yet used the model nor
determined all the uses to which they might put the model, they
identified as their most likely uses (1) comparing the benefits and costs of
making alternative highway improvements, (2) developing or refining state
transportation investment plans, and (3) assessing highway needs forecast by
state district offices or local agencies. They further mentioned the
possibility of using the model to produce planning and management tools such
as long- range state highway plans.
If the HERS- ST pilot project shows that states view the HERS- ST model as a
useful tool, FHWA expects to upgrade the model for future users. In doing
so, it would consider both enhancements that have already been planned
for the national- level HERS model and changes targeted specifically to
HERS- ST. Enhancements planned for the national- level HERS model that could
be incorporated into HERS- ST include an improved approach for
calculating the long- term benefits of improvements, an improved method of
pavement analysis, and upgrades to the model's vehicle emissions data.
Changes specifically to improve the HERS- ST model's usefulness to states
might include converting the model to a menu- driven system to improve its
ease of use or revising the model's data input format so that it matches
FHWA's current state highway data reporting requirements. Our interviews
with state officials also indicated that states might want to analyze more
detailed highway information than HERS- ST now considers.
Background DOT submits biennial reports, called Conditions and Performance
Reports, 2 to the Congress, detailing the state of the nation's highways,
bridges, and other surface transportation systems along with investment
requirements for these systems. In developing its portion of the report,
FHWA bases its estimates of investment requirements for most highways on the
Highway Economic Requirements System (HERS) computer model.
Before using the HERS model, FHWA used an engineering model that compared
highway conditions with engineering standards, identified deficiencies, and
calculated investment needs by totaling the costs of fixing all the
deficiencies. In contrast, the HERS model compares the relative costs and
benefits associated with potential highway improvements, such
as widening or resurfacing, to identify those that are economically
justified. The HERS model begins by assessing the current condition of the
highway sections in its database. It then projects the future condition and
performance of the highway sections on the basis of expected changes in
factors such as traffic, pavement condition, and average vehicle speed.
(See fig. 1.) The model identifies deficient highway sections, ranks
improvements by economic merit (benefits exceeding costs), and then selects
improvements. Benefits considered include reductions in factors like travel
time, vehicle operating costs, accidents, and vehicle emissions over the
lifetime of the improvement, while costs considered include the capital
expenditures required to construct the improvement. 3
2 The most recent report in the series was 1999 Status of the Nation's
Highways, Bridges, and Transit: Conditions & Performance, DOT (FHWA- PL- 00-
016, May 2000). 3 The technical specifications for both models are
documented in Highway Economics Requirements System Technical Report DOT
(FHWA, June 2000).
Figure 1: Simplified Representation of the HERS Modeling Process Assemble
Forecast
Identify Select
Combine highway data
future Identify
economically section
section (traffic
condition and deficient
justified improvements
improvement forecasts,
performance sections
improvements that satisfy
costs to highway of highway for deficient
investment develop needs
conditions, etc.) sections
sections criteria
estimates
Source: FHWA data.
The total cost of constructing selected improvements represents the future
investment requirement for highways included in the HERS model. FHWA can
calculate these costs on the basis of several different scenarios. For
example, under the “economic efficiency” scenario, the model
selects and implements all the improvements for which benefits exceed costs.
Under the “maintain current (pavement) conditions” scenario, the
HERS model selects and implements the least costly mix of improvements that
would
maintain average pavement conditions. Under a third scenario, designed to
address road congestion, the HERS model selects the least costly
improvements that would maintain current travel times.
To run the HERS model, FHWA uses highway condition and performance data that
each state collects and annually updates on a sample of highway sections 4
representing different highway classes. 5 The highway sections range in
length from 1 block to 10 miles. States are to report detailed highway data
for sampled 6 highway sections. The data include information on highway
capacity, traffic volume, pavement roughness, lane widths, and 4 The HERS
model is also capable of analyzing all sections in the highway classes it
models. When the model uses a sample of highway sections, it also uses
“expansion factors” that extrapolate highway conditions and
improvement costs to a state or national level. 5 FHWA maintains the
resulting database, known as the Highway Performance Monitoring System
(HPMS). The nine classes of highways reported for FHWA's HPMS database are
(1) urban interstates, (2) rural interstates, (3) urban freeways and
expressways, (4) urban other
principal arterials, (5) rural other principal arterials, (6) urban minor
arterials, (7) rural minor arterials, (8) urban collectors, and (9) rural
major collectors. The three FHWA highway classes not reported for FHWA's
HPMS database are (1) urban local roads, (2) rural local roads, and (3)
rural minor collectors. 6 In 1997, states reported detailed data for 125,000
sampled highway sections. The number of sample sections was reduced to
112,000 in 1999.
other physical characteristics. In addition to collecting these data, the
states develop forecasts of traffic growth for each section.
We reviewed the HERS model and reported in June 2000 that HERS provided the
Congress with a more useful and realistic estimate of needed highway
improvements than earlier models had. In particular, we found that a major
strength of the model is its ability to assess the relative benefits and
costs associated with making alternative highway
improvements. In addition, an expert panel of economists and engineers from
the public and private sectors convened by FHWA in June 1999 found that FHWA
has strengthened HERS over time and that recent refinements have increased
the model's applicability and credibility. Nonetheless, we
found that the HERS model also has some limitations. First, since the model
analyzes each highway section independently rather than the entire
transportation system as a whole, it cannot reflect how changes in one part
of the system might affect another part of the system, such as how traffic
might be redistributed 7 as improvements are made. Second, the HERS
model uses a computational “shortcut” to approximate the
lifetime benefits associated with an improvement. Several transportation
modeling experts have questioned whether this approach reasonably
approximates future benefits. Third, because the HERS model is not designed
to quantify the uncertainties associated with its methods, assumptions, and
data, the model cannot estimate the full range of uncertainty 8 within which
its estimates vary. Finally, the model excludes certain classes of the
nation's highways from its analysis, meaning that FHWA must use alternate
methods to forecast investment needs for these classes of highways. 9 7
Although the effect of this limitation is unclear, explicitly modeling the
entire
transportation network is not possible with the current state of the art in
modeling or available data. The HERS model incorporates the concept of price
elasticity, which FHWA officials believe captures the net effect of all
changes in the transportation network. The model uses price elasticity to
assess the response of drivers to changes in the cost of traveling on a
highway, partly mitigating the benefits of a highway improvement. For
example, because improving a highway lowers travel costs, some drivers may
respond by driving more often. As a result, traffic on the improved highway
may increase more quickly than anticipated, reducing the future benefits of
the improvement. 8 In its 1999 biennial report on investment requirements,
FHWA accounted for some uncertainties by doing “sensitivity
analyses” to measure how much its HERS estimates change when the value
of certain key inputs or assumptions used in the model are changed.
9 The HERS model does not analyze the three classes of roads that are not
included in FHWA's database: rural minor collectors, rural local roads, and
urban local roads. Furthermore, HERS does not estimate investment
requirements for possible new roads.
Like FHWA, state departments of transportation undertake planning and
reporting activities to manage their highways and determine their capital
needs. For example, under federal transportation planning requirements,
states must carry out a process for considering the effect of transportation
projects on a variety of factors, including the economy and the environment.
States are also required to develop both long- range plans
covering at least 20 years and transportation improvement programs (state
investment plans) that cover at least 3 years. These requirements help
ensure that state transportation projects come from a systematic planning
process rather than from a “wish list” of transportation
projects. To meet these planning and reporting requirements, some state DOTs
have had to rely on their technical capabilities. Many states have developed
pavement management systems to help them systematically analyze data on
existing
highways and project future pavement needs. For example, several states have
used models, based on pavement engineering criteria, to analyze pavement
needs either at the project level or for a whole statewide network. Some
states have also adopted a predecessor of the HERS model developed by FHWA,
called the Analytic Process model, that compares highway conditions with
engineering criteria to identify potential improvements.
After FHWA developed the HERS model, two states contracted to have
customized state- level HERS models developed for them. Oregon DOT, when
updating its long- range statewide highway plan, hired the same consultant
that had produced HERS for FHWA. That consultant recommended that Oregon DOT
use a customized version of the HERS model for its statewide plan.
Similarly, when Indiana DOT engaged the same consultant for a corridor
planning study, 10 the consultant recommended that Indiana DOT use a
customized version of the HERS model for its corridor planning analysis.
Indiana DOT subsequently used its model's results to draft a new statewide
highway plan.
10 Corridor planning studies examine the feasibility of future highway
improvements. A corridor connects significant end points and typically is
longer than any single highway project. Corridor studies are initiated well
in advance of specific improvement projects, allowing a highway agency to
secure or preserve rights- of- way before any actual projects are initiated.
FHWA Developed the After its positive experience with the national- level
HERS model and the
HERS- ST Model as an model's successful adaptation in Oregon and Indiana,
FHWA began to formally develop HERS- ST in 1999. FHWA expects that states
will use the
Investment Analysis model in a variety of ways to facilitate planning for
highway investment. Tool for Highway
Planning at the State Level
The National- Level HERS Our review of the national- level HERS model showed
that its results Model Produces Useful provide legislative and executive
branch officials with useful information Information About Highway
for decisions about highway investments. Legislative branch officials said
Investments
they use the estimates to obtain general information on the nation's need
for infrastructure investments and find the HERS estimates more useful than
previous estimates that were based on engineering analyses alone. FHWA views
the national- level HERS model as a step forward in its efforts to meet the
statutory requirement to report on the conditions and performance of the
nation's highways and future national highway investment requirements. FHWA
officials also said that the HERS model's benefit- cost approach complies
with an executive order 11 that requires federal spending for infrastructure
to be based on a systematic analysis of
expected benefits and costs. FHWA concluded that state transportation and
other officials might find HERS- type analysis helpful in analyzing highway
investments as well as supporting federal planning requirements.
Two States Are Using Facing increased funding constraints along with a
greater demand for Customized Versions of the expenditure accountability,
Oregon officials made use of a customized
HERS Model HERS model to prioritize needs and determine deficiencies in its
highway system. 12 Oregon officials cite their HERS model's effective use of
benefitcost analysis as a foundation for determining the best combination of
11 Executive Order 12893, Principles for Federal Infrastructure Investments
(1994), discusses
the importance of continuous infrastructure investment to sustained economic
growth. The order directs federal agencies with infrastructure investment
responsibilities to plan for investments using a systematic analysis of
expected benefits and costs.
12 Oregon received its customized version of the HERS model in early 1998.
improvements and for allocating resources between programs. Oregon officials
have found these benefit- cost results useful for highway planning, corridor
planning, and goal setting. For example, when analyzing the 1999 Oregon
Highway Plan (an element of the required long- range plan), state officials
evaluated investment tradeoffs between system preservation projects- capital
projects that ensure that a highway continues to serve its intended purpose-
and modernization projects- capital projects that typically increase
capacity. Oregon's report said that this analysis helped
the Oregon Transportation Commission gain a clear picture of the condition
of the highway system under different funding scenarios and thus helped the
Commission make difficult investment decisions. (See app. II for information
on the technical features of the Oregon model.)
Indiana's DOT sought out a modified version of the HERS model in an attempt
to improve its planning process and, more specifically, to strengthen its
technical planning tools. 13 Indiana officials wanted a model that would
analyze benefits and costs for all of the state's highway projects,
and they decided that a modified version of the HERS model would meet their
needs. These officials used their HERS model to analyze highway investment
needs over a 25- year period, including a comparison of the status of the
highway system at different levels of funding. In addition, Indiana
officials used their model to analyze highway investment needs at the
district level within the state. The Indiana model has a unique feature
that links specific model results with a geographic information system (GIS)
that visually displays results on state highway maps. This feature allows
the staff to compare district offices' and metropolitan planning
organizations' priorities with the ones the model identifies. (See app. II
for information on the technical features of the Indiana model.)
13 Indiana received its customized version of the HERS model in 1998.
FHWA Developed the After FHWA officials reviewed their positive experience
with HERS, along
HERS- ST Model to Help with the positive experiences of Oregon and Indiana
with their customized States Plan and Manage HERS models, they decided to
consider developing a HERS model that all
states could use. FHWA's Office of Asset Management 14 commissioned two
Their Highways
studies to identify the potential role of a HERS model in helping states
assess their highway investment needs and develop state highway plans. The
studies demonstrated a potential state interest in a state- level HERS
model. Therefore, FHWA developed a prototype state model, HERS- ST, from the
national- level HERS model that any state could use for planning and
programming activities. FHWA officials believe that states could use the
HERS- ST model to perform benefit- cost analysis on highway improvements and
to forecast the future condition and performance of state highway systems.
In addition, the Office of Asset Management's Asset
Management Primer 15 explains that HERS- ST has the potential to help state-
level policy makers address resource allocation questions because the model
can analyze “what if” questions using specific funding levels.
For example, the model can show the long- term effects that different levels
of spending or different emphases in investment could have on the condition
and performance of highways. The primer also states that the model may even
help some states meet new Government Accounting Standards Board provisions
requiring states to report the cost of maintaining their transportation
infrastructure assets. 16 The HERS- ST model that FHWA developed is based on
and operates in much the same way as the national- level HERS model, with a
few noteworthy differences. Like the HERS model, HERS- ST (1) projects the
future condition and performance of a state's highway system, (2) assesses
whether any highway improvements are warranted, and (3) selects 14 FHWA
established the Office of Asset Management in February 1999 to help states
systematically manage and analyze their highway assets. FHWA is to encourage
states to systematically analyze the benefits and costs of highway
infrastructure investments, according to Executive Order 12893. 15 Asset
Management Primer, DOT (FHWA- IF- 00- 010, Dec. 1999). 16 Starting in 2001,
state governments will have to follow a new accounting standard, known as
GASB Statement No. 34, that generally requires governments to report their
infrastructure assets at historic cost and depreciate them over time. Since
depreciation may
not always be appropriate, the rule also allows governments with adequate
asset management systems to disclose the estimated amount required each year
to maintain and preserve their assets. The HERS- ST model may help
governments follow this second approach.
appropriate improvements using benefit- cost analysis. One difference
between the HERS and HERS- ST models is that the HERS- ST model has an
“override” feature that allows a state official to override
highway improvement selections made by the model in order to reflect
specific, local conditions. According to FHWA officials, the model's
override feature will enable state officials to apply specific knowledge
about highway improvements (such as whether implementing a particular
improvement is feasible) that may not be reflected in the model's database.
For example, an official might specify that the model reconstruct a highway
section rather than resurface it because of problems with the underlying
structure of the
pavement that are not yet apparent from measurements of the pavement's
roughness. The override feature is unique to the HERS- ST model. Another
difference is that the HERS- ST model is capable of providing detailed
results about each of the highway sections it analyzes, including
information on the particular improvement selected, the expected future
condition of the section, and the benefits and costs of making the
improvement. By contrast, the HERS model generates only summary results for
the classes of roads it analyzes.
In addition to these differences between the two models, the HERS- ST model
offers states further options regarding what data to consider. State
officials can adjust the HERS- ST model to reflect state conditions by, for
example, using state highway construction costs rather than national average
costs. And state officials may use HERS- ST either to analyze the
statistical sample of their state's highways included in FHWA's Highway
Performance Monitoring System (HPMS) database or, if they have the
appropriate data, to analyze all highway sections in the state's system.
While the HERS model could also analyze all highway sections, it is
currently limited to analyzing only the sample of sections in the HPMS
database. When the HERS- ST model's projections are based on sampled
sections in the HPMS database, the projections may not account for all the
highways for which a state department of transportation is responsible. 17
However, the state can, if it has appropriate data on all its highway
sections, use the HERS- ST model to analyze every section in the state
highway system, as Oregon and Indiana did with their customized HERS
17 The sample data may exclude highways for which the state is responsible,
like local roads or rural minor collectors, or include highways for which
the state is not responsible. For example, according to an Indiana official,
Indiana's sample data addresses 30, 000 miles of highway, of which only 12,
000 miles are within state jurisdiction.
models. (See app. II for a more detailed comparison of the national- level
HERS and HERS- ST models.) FHWA Provided HERSST FHWA distributed the
prototype HERS- ST model software to 20 states
to States Through a volunteering to participate in its pilot project, which
is intended to gauge
interest in the model and to further identify potential uses for and
revisions Pilot Project to it. Interest in the model was higher than FHWA
expected. According to an FHWA official, the agency expected to have five
states participate in the
pilot. However, the number of interested states grew to 20, including
Indiana and Oregon, before the pilot began. (See fig. 2.) Indiana and Oregon
officials said they wanted to participate in the pilot program to learn
about new features incorporated into the HERS- ST model and to share their
customized HERS model experience with other pilot states.
Figure 2: States Participating in the HERS- ST Pilot Program
Pilot states (as of Dec. 11, 2000)
Source: FHWA information.
In December 2000, FHWA distributed the model, along with technical manuals
and state- specific sample data on highway sections needed to run the model,
to the 20 pilot project states. This distribution took place about 2 months
before the pilot's February 2001 kickoff workshop in New Orleans, Louisiana.
The workshop was designed to train participating
states in the use of the HERS- ST model. It included general information on
the use of the model, information on Indiana's and Oregon's experiences with
their customized HERS models, and technical review and training. FHWA
officials plan to focus their efforts during the pilot program on providing
technical support to participating states. FHWA officials also
hope to provide training for state policymakers to explain how the HERSST
results can be used.
FHWA anticipated that the pilot project would conclude after approximately 2
months. However, the agency was prepared to extend the duration of the pilot
if states indicated that additional time would be helpful. At the conclusion
of the pilot, participants will be asked to report on (1) their experiences
testing the model, (2) their assessment of the model's usefulness in state
planning and programming activities, and (3)
their recommendations for further FHWA initiatives with respect to the
model. FHWA expects to report by August 2001 on states' comments and its own
recommendations for further HERS- ST model initiatives. FHWA officials said
that the agency will consider changes to the HERS- ST model
at the end of the pilot project, depending on the number of states that
identify particular changes as important.
States Participating in Officials from almost all of the eight states we
randomly selected 18 FHWA's Pilot Project indicated that although they had
limited knowledge about HERS- ST, they
were looking forward to expanding their states' technical tools to better
Expect to Use HERSST support their planning processes. When asked why they
planned to to Supplement participate, the state officials said that, while
they did not have details of Their Planning Tools how the model works, they
did not want to miss out on any tool that might improve their planning and
highway management. In general, the state
With Economic officials also expressed some level of dissatisfaction with
their current Information planning tools. As one state official explained,
her DOT was always looking
to improve its planning process. (See app. III for the results of our
discussions with state officials about the HERS- ST model.)
A number of state officials indicated that the HERS- ST model's benefit-
cost analysis capability is an important feature that made the model
attractive to them. In response to a question about why states wanted to
participate in the pilot, officials from most of the states said that they
hoped the model would help improve their knowledge about the economic impact
of investment decisions. Officials from five of these states believe this
would help the states prioritize projects and maximize the effect of their
spending. An official in one state said that the state's highway funding
depends, in
18 See app. I for details of our methodology for selecting eight states to
interview from among the states considered likely to participate in the
HERS- ST pilot program when we contacted FHWA in September 2000.
part, on a study of infrastructure needs. However, the state's
infrastructure study is based on the assumption that highway funding is
unlimited. Thus, the official believes the results of the needs study are
unrealistic. The official hopes HERS- ST can contribute economic reality to
the state highway funding plan.
When presented with a list of potential uses for the HERS- ST model results,
state officials we interviewed said that, if the model provided realistic
results, they would consider using the results in the following tasks: ?
comparing benefits and costs of making alternative highway
improvements; ? developing state highway plans, such as state transportation
investment
plans, long- range highway plans, local highway needs forecast assessments,
and corridor studies; ? satisfying the requirements of the Government
Accounting Standards
Board's provisions for reporting on the value of transportation
infrastructure assets; ? allocating funds to offices within the state
highway agency (for example,
by district). (See app. III for a more detailed list of potential uses.) For
example, one state official indicated that his state plans to update its
long- range highway plan shortly and hopes that HERS- ST may be useful for
that work. Overall, officials indicated that the three most important uses
for their states would probably be (1) performing benefit- cost analysis of
alternative highway improvements, (2) developing or refining state
transportation investment plans, and (3) assessing highway needs forecast by
state district offices or local agencies.
Potential If states involved in the pilot project find that the HERS- ST
model is useful, Improvements to the
FHWA expects to upgrade it for future state users. First, FHWA plans to make
certain changes to the HERS- ST model to keep it current with HERS- ST Model
analytical improvements planned for the national- level HERS model. Second,
FHWA is considering changes designed to make the model easier for states to
use. Finally, states might also ask that FHWA enhance the HERS- ST model so
it can analyze more detailed highway information. FHWA Plans to Upgrade
According to FHWA officials, if the pilot participants find the HERS HERS-
ST
concept attractive, FHWA will, as appropriate, provide for revising the
HERS- ST model so that it will benefit from upgrades to the national- level
version of the model. FHWA officials said their improvement plans for the
national- level version of HERS include eliminating the computational
shortcut that we identified as a limitation in our June 2000 report. This
shortcut is designed to approximate the lifetime benefits associated with a
highway improvement. However, the approximation may not fully represent the
lifetime benefits, and FHWA officials acknowledge that improvements in
computing power have made it unnecessary. FHWA also plans to change the
national- level HERS model by
? incorporating pavement performance data based on climate zones instead of
assuming one rate of pavement deterioration, ? revising its highway-
capacity analysis to reflect changes in the Transportation Research Board's
Highway Capacity Manual,
? revising the emissions data used as soon as the Environmental Protection
Agency finishes revising its emissions model, and ? updating pavement
improvement costs, currently based on 1988 data, to represent 1998 or 1999
data.
HERS- ST Could Be Modified As part of its evaluation of the pilot project,
FHWA plans to ask state to Make the Model Easier officials for suggestions
of potential improvements to the model. Assuming for States to Use
the project continues past the pilot phase, FHWA officials say they will
consider making those changes that will benefit multiple states. Our
interviews with state, FHWA, and other officials indicate that states may
ask FHWA to modify HERS- ST in ways that make the model easier to use
without altering the model's analytical structure. One state official
expressed concern over the user- friendliness of the model, having heard
that the HERS- ST program is not user- friendly because it operates in an
older DOS- based computer environment that department staff might not be
familiar with. An FHWA consultant reviewing the HERS model concluded
that updating the model so that it can operate in a more user- friendly
menudriven environment might be the key to increasing the number of states
that use the model. FHWA officials agreed that a menu- driven program
would make the model easier for states to use. The HERS- ST model would also
be easier for states to use if it accepted highway data in the same format
that states use in their annual data submissions for FHWA's HPMS database.
The HERS- ST model requires input in the 1993 data reporting format, not the
current HPMS format. To assist states participating in the pilot project,
FHWA provided each one with its highway data already reformatted for use
with the HERS- ST model. However, state officials wishing to analyze other
highway sections in their
states would have to reformat their data to the older format before the
model could use it. An FHWA consultant, commenting on ways that the HERS
model could be more useful to states, recommended that the model
accept data corresponding to the latest format that FHWA requires for state
HPMS data submissions. FHWA officials recognize that widespread use of the
HERS- ST model would require addressing this situation. HERS- ST Could Be
Modified Our interviews with state and FHWA officials indicate that some
states to Better Fit States' Analytic
would like the HERS- ST model to analyze more detailed pavement Needs
management data. Many states have developed sophisticated pavement
management systems that analyze more data than the pavement deterioration
analysis done in the HERS or HERS- ST models. For example, a number of
states already have pavement management systems that consider several types
of pavement distress data. HERS- ST, like the HERS
model, relies on data states report in the form of the International
Roughness Index 19 or the Present Serviceability Rating. 20 Officials from
four of the states we spoke with reported that they collect both roughness
index data and serviceability rating data. However, these officials noted
that they do not use roughness index data for planning purposes, preferring
to rely on their serviceability rating or the other data for highway system
planning. Officials from half of the states we contacted said they only
collect roughness index data at FHWA's request and they base their internal
planning analysis on pavement rating data in their pavement management
systems. In addition, officials from two states said they were not satisfied
with the quality of their states' roughness index data and preferred to rely
on their pavement rating data.
FHWA officials also said they expect to address some of these concerns by
incorporating more pavement distress data in the HERS model at some 19 The
roughness index is based solely on surface roughness measurements. Most
states
collect these data with specially equipped vans traveling at highway speeds.
FHWA instructs states to report the roughness index for all the major roads
in the country. FHWA encourages states to report the index for all other
highway sections sampled for the national highway database. 20 The
serviceability rating is a subjective approach for quantifying pavement
condition. Prior to 1993, FHWA asked states to report the serviceability
rating for all highway sections in its national highway database. FHWA still
allows states to report serviceability ratings for
highway sections in its national database that are not major roads. If a
state reports both roughness index data and serviceability rating data to
FHWA, the HERS model uses the roughness index data for analysis.
point in the future. However, they will not do so until such data are
available to FHWA from all the states. 21 FHWA officials said they are
willing to support only one version of the HERS- ST model. But because
states use various pavement distress measures, it is not clear to FHWA
officials whether including these additional pavement data in the HERS- ST
model
would satisfy all states' concerns. Agency Comments and
We provided a draft of this report to the Department of Transportation for
Our Evaluation
review and comment. Officials from the Department generally agreed with the
report. These officials also provided technical and clarifying comments,
which we incorporated into the report as appropriate.
We conducted our review from June 2000 through February 2001 in accordance
with generally accepted government auditing standards. We will send copies
of this report to cognizant congressional committees; the Honorable Norman
Y. Mineta, Secretary of Transportation; and the Administrator, Federal
Highway Administration.
If you or your staff have any questions about this report, please contact me
at (202) 512- 2834. Appendix IV lists key contacts and contributors to this
report.
Phyllis F. Scheinberg, Director, Physical Infrastructure Issues
21 Officials from the states we spoke with reported that their pavement
planning data include pavement condition measures beyond roughness, such as
rutting, cracking, and faulting. The American Association of State Highway
and Transportation Officials recently developed standards for roughness,
rutting, and faulting and is developing a standard for cracking.
Appendi Appendi xes x I
Scope and Methodology To determine why the Department of Transportation's
(DOT) Federal Highway Administration (FHWA) developed a state- level version
of the Highway Economic Requirements System (HERS) computer model and how
FHWA expects that states will use the model, we first reviewed our work and
resulting June 2000 report on the strengths, limitations, and uses of the
national HERS model. We then interviewed FHWA officials about their state-
level HERS model (HERS- ST). We also reviewed FHWA documents about the HERS-
ST model and projects in FHWA's Office of
Asset Management. Finally, FHWA officials and HERS contractors told us that
two states- Indiana and Oregon- were using state- level HERS models. We
visited Indiana and Oregon to discuss the use of these models with officials
in the Indiana and Oregon state departments of transportation and obtained
and reviewed available model documentation and state products generated
using their HERS models.
To determine how FHWA is making the state- level HERS model available to
states, we spoke with FHWA officials about their pilot- project plans. We
also reviewed the pilot project workshop agenda and attended the
workshop in February 2001. We reviewed HERS- ST model documents, including
the draft Highway Economic Requirements System Technical Manual and the
draft Highway Economic Requirements System Users Manual, and we talked with
model developers to determine how the model
was developed. Finally, we reviewed FHWA's evaluation plan for the HERSST
pilot project and the time frame for the project.
To determine how states expect to use the HERS- ST model and its results, we
reviewed reports by FHWA consultants on the potential role of HERS in state-
level investment decisions and talked with officials from a random selection
of 8 of the 16 states that planned to participate in FHWA's pilot project.
The 16 states represent all states that FHWA reported were planning on
participating in FHWA's pilot program as of September 5, 2000, with the
exception of Indiana and Oregon. We excluded Indiana and Oregon from this
random sample because both states are already using customized state- level
HERS models, and we were already planning to conduct site visits for these
two states. Table 1 shows the 8 states we
contacted, as well as the 16 states from which we chose the sample.
Table 1: HERS Pilot Project States and Eight States Randomly Selected for
Interviews
Universe of states and selected states Arizona Missouri Arkansas Nebraska
Delaware New Jersey Florida New Mexico
Iowa Ohio
Louisiana Pennsylvania
Maine Rhode Island
Michigan Utah
Note: These 16 states represent the states that were included in FHWA's
pilot project as of September 5, 2000, with the exception of Indiana and
Oregon. Randomly selected states are in bold.
Source: FHWA information.
To obtain consistent information from the eight states we contacted, we used
a semi- structured interview format. See appendix III for a copy of the
interview document with the results of our discussions with the eight
states. As of December 11, 2000, the number of states that planned to
participate in FHWA's HERS- ST pilot had grown to 20. See figure 2 in the
letter for a map of the 20 states. To identify potential changes that could
be made to the model, we discussed this issue with a wide variety of groups,
including FHWA officials, the consultant who developed the HERS- ST and the
Indiana and
Oregon HERS models, state officials using the Indiana and Oregon models,
state officials planning on using the HERS- ST model, and others, such as
academics, who have used the HERS model. We also reviewed information
on pavement measurement data, including our previous work on pavement
measures. 1 1 Transportation Infrastructure: Better Data Needed to Rate the
Nation's Highway Conditions (GAO/ RCED- 99- 264, Sept. 27, 1999).
Appendi x II
Information About HERS Models This appendix describes technical aspects of
the HERS computer model and the three related models designed for use by
state highway planners. FHWA's HERS Model The HERS model simulates
infrastructure improvement decisions for the highways it models by comparing
the relative benefits and costs associated with alternative improvement
options. In conducting its analysis, HERS
uses an extensive set of data that are primarily collected and updated by
the states and maintained by FHWA in the Highway Performance Monitoring
System database. In addition, the HERS model performs its analysis using
several submodels representing specific highway processes, including traffic
growth, pavement wear, vehicle speed, accidents, and highway improvement
costs. The analysis, which is based on the current condition of the highway
system, is conducted over four 5- year periods, for
a total of 20 years. The HERS model draws information from the database and
analysis from the submodels to identify deficient sections, evaluate
alternative improvement options, and select and implement improvements. HERS
uses benefit- cost ratios (benefits divided by costs) to evaluate and select
improvements under several investment scenarios that FHWA developed. The
benefits include reductions in travel times, vehicle operating costs, and
agency maintenance, while the costs include the
capital expenditures necessary to construct the improvement. The model
reports its results in a series of tables showing the cost of improvements
needed to support the model's investment decisions for each highway class
and funding period analyzed. The HERS model has several strengths: ? The
model's major strength is its ability to assess the relative benefits and
costs associated with alternative options for making improvements on the
nation's highways. The HERS model selects for implementation only those
improvements that are economically justified according to its
analysis, a significant improvement over FHWA's previous methods, which used
engineering standards to identify deficiencies and select improvements
without regard to economic merit. ? Another strength of the HERS model is
that FHWA has consulted with
experts in order to assess the model's reasonableness and improve it. For
example, in June 1999, FHWA convened an expert panel consisting of
economists and engineers from the public and private sectors. This panel
found that FHWA has strengthened the model over time and that the recent
refinements have increased its applicability and credibility.
The HERS model has some limitations: ? First, because the HERS model
analyzes each highway section
independently rather than the entire transportation network, it cannot
completely reflect changes occurring among all highways and modes in the
transportation network at the same time. For example, it will not reflect
how, as improvements are made, traffic might be redistributed
from other existing highway sections to an improved highway section. By
incorporating price elasticity into the model, FHWA officials assume that
the model captures the net effect of all changes in the transportation
network as well as in the overall economy. Although the implication of this
limitation is unclear (it may over- or under- state the effect of changes in
traffic resulting from a highway improvement), explicitly modeling the
entire transportation network is not possible with the current state of the
art in modeling or available data. ? Second, because the HERS model is not
designed to quantify the
uncertainty associated with its methods, assumptions, and data, the model
cannot estimate the full range of uncertainty within which its estimates
vary. As a result, the precision of the model's estimates is unknown. The
HERS model's estimates rely on a variety of estimating techniques and
hundreds of variables, all of which are subject to some
uncertainty. However, changing the model to fully account for uncertainty in
its factors is not likely to be cost- effective because it could require
extensive and expensive reprogramming. We recommended in our June 2000
report that FHWA clarify, when
publishing the results of HERS model analyses, that there is uncertainty
associated with the results. State- level users can account for some
uncertainty by conducting “sensitivity analyses” to measure how
much the model estimates change when the values of certain key inputs or
assumptions used in the model are changed.
? Third, the HERS model uses a computational “shortcut” to
approximate the lifetime benefits associated with an improvement.
Conceptually, benefits such as reductions in travel time accrue over each
improvement's full lifetime, 20 years or more. However, in its initial
evaluation of whether to improve a highway section, the HERS model
calculates benefits only during the first 5- year period. To account for the
benefits accruing after the first 5- year period, FHWA developed a shortcut
that essentially uses an estimate of the improvement's construction cost as
a proxy for the improvement's remaining future benefits. 1 FHWA developed
the shortcut several years ago, when limitations in computer processing
power necessitated simplifying some of the calculations. Given recent
improvements in computing power, FHWA officials plan to modify the HERS
model to account for lifetime
benefits and see correcting the shortcut as a potential improvement for the
HERS- ST model as well. ? Fourth, although FHWA has taken steps to ensure
that the data used in the HERS model are reasonable, some of these data vary
in quality. For
example, the model uses emissions data that may not be representative of
actual conditions. To estimate the emissions associated with traffic on a
given section, the model uses information from the Environmental Protection
Agency (EPA) on emissions rates per vehicle type and speed.
Vehicle emissions, however, may depend more on how the vehicle is driven
than on the total miles driven. FHWA officials told GAO they will update
these data once EPA finishes revising its emissions data. In addition, we
reported earlier that the pavement roughness data reported by the states to
FHWA are not comparable, partly because the states use different devices and
approaches for measuring roughness. 2 The HERS model uses the roughness data
in projecting the pavement condition of each section. FHWA is supporting
efforts to standardize states' pavement roughness measurements. Moreover,
some information used in the model is dated. For example, the pavement
resurfacing costs used
in the HERS model are based on 1988 data (adjusted for inflation from 1988
to 1997). FHWA officials said they plan to update the HERS model's
resurfacing costs, and the HERS- ST model offers users the option of
introducing their own construction cost data.
1 With this shortcut, the HERS- ST and HERS models assume that the remaining
future benefits of an improvement can be approximated by the costs that
would be avoided by making the improvement in the current 5- year period. 2
Transportation Infrastructure: Better Data Needed to Rate the Nation's
Highway Conditions (GAO/ RCED- 99- 264, Sept. 27, 1999).
HERS Model Used in The Oregon Department of Transportation obtained the
first customized Oregon HERS model in 1998. Oregon hired a consulting firm,
Cambridge
Systematics, Inc., to help the state develop a long- range statewide highway
plan. The consulting firm, which also developed the HERS model for FHWA,
worked with Oregon officials to customize the HERS model, which resulted in
the creation of HERS/ OR. Oregon never received specific documentation for
its model. But according to Oregon officials and the consultant, the model
differs from the national- level HERS model in the following ways:
? HERS/ OR allows the user to override the model's improvement decisions for
specific sections, for example, for a road that cannot feasibly be widened
due to a nearby mountain. ? HERS/ OR's output includes two innovations: a
section- by- section report providing details on individual improvements for
each segment for each
funding period and a revised summary table of improvements for the state's
four unique highway classifications. ? HERS/ OR's procedures for analyzing
price elasticity are rudimentary
when compared with the current HERS model, and data on vehicle accident
costs are older. HERS Model Used in The Indiana Department of Transportation
contracted in 1998 for a Indiana customized HERS model known as HERS/ IN.
HERS/ IN is also similar to HERS, but has more unique features than HERS/
OR: ? HERS/ IN, like HERS/ OR, analyzes all sections of its state highway
system. ? HERS/ IN uses its own data on construction costs, allowing the
model to base its estimates of construction costs on more exact, local data.
? HERS/ IN is capable of using pavement improvement decisions from the
state's sophisticated pavement management system. However, Indiana DOT staff
had not used this feature by the time we conducted our work. ? Unlike the
national- level HERS model, HERS/ IN allows its user choices
for overriding modeled improvement decisions. For example, the user can
specify the type of improvement, its cost, its timing, and the improvement's
effect on highway capacity. Indiana DOT has not used this feature, according
to officials. ? HERS/ IN's output includes the basic national- level HERS
output tables,
plus section- by- section improvement tables like those of HERS/ OR and
tables that summarize highway improvements' benefits for users due to
decreased travel time, decreased operating costs, and increased highway
safety. In addition, HERS/ IN's output is used to generate maps to display
the location of its improvement plans. The model is designed to feed its
output data into a geographic information system software package that
produces maps of the model's proposed improvements.
The Indiana Department of Transportation officials said that this feature
improves their ability to display the location of the HERS/ IN model's
decisions to policymakers. Furthermore, the maps help the state staff
determine whether or not HERS/ IN's decisions are realistic. For example, if
two major improvements are proposed for nearby sections of highway, the maps
could alert the agency that, to avoid traffic
problems in that area, the projects should not be performed simultaneously.
? HERS/ IN is able to consider the construction of new highways that
might be needed to provide capacity for future travel demand. The Department
has a sophisticated travel- demand model that supports this HERS/ IN
feature. Found in no other version of the HERS model, this feature allows
Indiana DOT to specify new highways and the effect of
capacity improvements on traffic systemwide, as well as to compare
alternative improvements for addressing a capacity problem. Indiana DOT has
not used this feature, according to officials. ? Unlike the HERS model, the
HERS/ IN model is not used to assess the
effect of highway travel on the environment. According to state officials,
the HERS/ IN model could take environmental data into account when making
its decisions, but the officials did not feel this feature was feasible in
their model. The HERS- ST Model The HERS- ST model is the most recently
designed HERS model. Generally, HERS- ST offers the analytic approaches
available in the most recent HERS
model revision. Because it is based on the HERS model, it has the same
strengths and limitations that were noted above. However, the HERS- ST model
differs from the national- level HERS model in the following ways:
? Unlike the HERS model, the HERS- ST model has an “override”
feature that allows a user to override some or all of the improvement
decisions made by the model. For example, the user can specify the
particular type of improvement to be made on a highway section in any
particular
funding period. In the override mode, the model selects the userspecified
improvements regardless of whether they are economically justified.
According to FHWA officials, the model's override feature will enable state
users to apply specific knowledge about highway
improvements (such as whether implementing a particular improvement is
feasible) that may not be reflected in the model's database. ? In addition
to the override feature, the HERS- ST model differs from HERS in the number
of highway classes it can analyze and the level of detail of the results it
generates. For example, the HERS- ST model can
analyze highway sections from all 12 of FHWA's classes of roads, including
rural minor collectors and urban and rural local roads. The HERS model is
designed to analyze sampled sections from 9 of the 12 highway classes. Also,
the HERS- ST model is capable of providing the user with detailed results on
the highway sections it analyzes, including information on the particular
improvement selected, the expected future condition of the section, and the
benefits and costs of making the improvement. FHWA officials stated that
this feature would enable the state user to study what happens on individual
sections. By contrast, the
HERS model generates only aggregate results for classes of roads. ? Both the
HERS- ST and the HERS models also use data from studies of the national
economy. However, the state user can modify some of these
data to reflect conditions in his or her state. For example, both models
count as a benefit any reduction in travel time brought about by a highway
improvement. In making this calculation, FHWA uses average national hourly
compensation data from the Department of Labor's Bureau of Labor Statistics
to quantify the dollar value of travel time
saved by travelers on work- related trips. In the HERS- ST model, the state
user could substitute state- level data to derive an alternative estimate of
travel time savings. The HERS- ST model also offers the state user a choice
between analyzing a
statistical sample of highways represented in FHWA's HPMS database or the
option of analyzing all highway sections in the state's system.
State Use of the HERS While the HERS- ST model pilot project is FHWA's first
attempt to promote Model state use of a HERS model, the agency previously
released copies of the HERS model. The model's existence was well publicized
because it had
been described in DOT's biennial Conditions and Performance reports starting
with the 1995 edition, 3 it was profiled in studies, 4 and it was cited in
TEA- 21. By 1998, FHWA was providing HERS model documentation and computer
files to parties who requested them. FHWA reported that 18 requesters,
including state DOT officials, academics, and consultants, obtained copies
of the model between April 1998 and September 2000. Michigan DOT officials
who obtained copies of the model found that it did not suit their needs.
They said that the HERS model was not useful to them because it would not
handle all of the roads the department needed to study; available data would
need reformatting to work with the model; and
the results were aggregated at the network level, which was too general to
be useful for the state's purposes. On the other hand, a researcher at North
Dakota State University's Upper Great Plains Transportation Institute found
the HERS model useful for state- level applications. He analyzed intermodal
freight diversion (rail to truck or truck to rail) on behalf of two state
transportation agencies. He also used HERS equations to analyze rural
highway preservation for a third state transportation agency.
To compare key differences between the HERS model and related statelevel
models, see table 2.
3 1995 Status of the Nation's Surface Transportation System: Condition and
Performance, Report to Congress, DOT (FHWA- PL- 96- 007, Oct. 27, 1995). 4
The Economic Effects of Federal Spending on Infrastructure and Other
Investments, Congressional Budget Office, June 1998; Road User and
Mitigation Costs in Highway Pavement Projects, NCHRP Synthesis 269,
Transportation Research Board, National
Research Council, 1999.
Table 2: Key Differences Between the HERS Model and State- Level HERS Models
Model Feature Current HERS HERS- ST HERS/ OR HERS/ IN
Highway data Analyzes a statistical
Analyzes a statistical Analyzes all highway Analyzes all highway sections
sample of sections from the sample of sections from sections in state
highway
sections in state highway considered nation's highways in state's highways
in FHWA's system or a sample of system. FHWA's nine highest nine highest
highway sections. highway classifications.
classifications. State user can modify database to include data representing
all state highways. Cost of travel time Uses average national Uses average
national
Allows user to substitute Allows user to substitute hourly compensation data
hourly compensation data state- level data. state- level data. Indiana to
value travel time. to value travel time. Allows
DOT has not done so. state user to substitute state- level data for national
data.
Highway Uses FHWA price index for Uses FHWA price index for Allows user to
substitute
Uses state- specified improvement cost federal- aid highway
federal- aid highway state- level data. pavement costs that differ factors
construction, adjusted to construction, adjusted to
from those in HERS. correspond to particular
correspond to particular state. state. Allows state user to substitute more
specific state- level data for default
values. Vehicle crash costs Uses updated analysis Uses updated analysis Uses
older analysis Uses updated analysis developed for FHWA's developed for
FHWA's developed for FHWA's developed for FHWA's 1999 Conditions and
1999 Conditions and 1997 Condition and 1999 Conditions and Performance
Report.
Performance Report. Performance Report.
Performance Report. Air pollution Uses information based on Uses information
based on Does not address. Does not address. damages vehicle emissions data
vehicle emissions data from Environmental from Environmental Protection
Agency's Protection Agency's MOBILE5a model.
MOBILE5a model. Price elasticity Uses rigorous approach to Uses rigorous
approach to Uses rudimentary Uses rudimentary
assess effect of changes in assess effect of changes in procedure to assess
effect procedure to assess effect travel cost on drivers' travel cost on
drivers' of changes in travel cost on of changes in travel cost on behavior.
behavior. drivers' behavior. drivers' behavior.
Model output about Generates improvement Generates improvement
Generates section- by Generates section- by
improvements cost data for each of nine cost data for each of nine section
report for each section report, plus maps highway classifications. highway
classes and for funding period, plus tables
to illustrate improvements. Cost of individual sections each section.
summarizing the state's Also creates tables of user
is not reported. four highway
benefits (travel time, classifications.
operating cost, and safety).
(Continued From Previous Page)
Model Feature Current HERS HERS- ST HERS/ OR HERS/ IN
User override mode Allows user to specify Allows user to specify type,
Allows user to specify type Allows user to specify type,
conditions under which cost, effect, and timing of
and timing of an cost, effect, and timing of
improvements would be an improvement. improvement for two
an improvement. mandatory. This feature is funding periods. not used for
FHWA's Conditions and Performance reports.
Model can analyze Does not allow user to Does not allow user to Does not
allow user to Allows user to specify new new highways specify new highway
specify new highway
specify new highway highway projects to be projects to be implemented
projects to be implemented projects to be implemented implemented in future
in future years. in future years. in future years. years. Indiana DOT has
not
done so.
Questionnaire for States That Asked to Participate in FHWA's Pilot Program
for the
Appendi x II I State HERS Model
Appendi x V I GAO Contacts and Staff Acknowledgments GAO Contacts Phyllis F.
Scheinberg (202) 512- 2834 Katherine Siggerud (202) 512- 2834 Staff
In addition to those named above, Richard Calhoon, Catherine Colwell,
Acknowledgments Timothy J. Guinane, Luann Moy, Judy K. Pagano, and Raymond
Sendejas made key contributions to this report.
(348251) Lett er
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Appendix I Scope and Methodology
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Appendix II Information About HERS Models
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Appendix III Questionnaire for States That Asked to Participate in FHWA's
Pilot Program for the
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Appendix IV
United States General Accounting Office Washington, D. C. 20548- 0001
Official Business Penalty for Private Use $300
Address Correction Requested Presorted Standard
Postage & Fees Paid GAO Permit No. GI00
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