The Highway Economic Requirements System: an introduction to HERS.Introduction
In 1989 the Chairman of the U.S. House of Representatives Committee on Public Works public works
Construction projects, such as highways or dams, financed by public funds and constructed by a government for the benefit or use of the general public.
Noun 1. and Transportation called for the "Department of Transportation (DOT) to accelerate its efforts to examine the costs, benefits and national economic implications associated with a broad array of [highway] investment options." (1)(1)
The DOT now has a model which simulates improvement selection decisions based on the relative benefit/cost merits of alternative improvement options. The newly developed Highway Economic Requirements System (HERS) uses incremental Additional or increased growth, bulk, quantity, number, or value; enlarged.
Incremental cost is additional or increased cost of an item or service apart from its actual cost. life-cycle benefit/cost analysis to define the "near-optimal" cost-effective set of appropriate improvement options given user defined Any format, layout, structure or language that is developed by the user. policy scenarios. (2)
HERS is designed to select the "best" improvements, reducing the total cost incurred by highway users and agencies while ensuring an acceptable economic return on the investment of public funds See Fund, 3.
See also: Public . The model recognizes reductions in direct user costs (travel time, incidents and vehicle operating costs operating costs npl → gastos mpl operacionales ) as highway-user benefits. Also considered as benefits are reductions in maintenance costs and the "residual value Residual value
Usually refers to the value of a lessor's property at the time the lease expires.
The price at which a fixed asset is expected to be sold at the end of its useful life. " of an improvement.
HERS procedures represent a dramatic change in traditional, National level, highway investment analysis. Other investment decision simulations are not sensitive to user benefits and are not intended to produce "optimal" solutions through the economic comparison of numerous alternatives.
This article provides an introduction to the logic design and capabilities of the HERS model. Initial HERS information will be reported in the upcoming 1993 Status of the Nation's Highways, Bridges and Transit Systems: Conditions and Performance Report to Congress (C&P Report).
The HERS model is distinguished from traditional highway investment analysis by two important features: The analytical technique An analytical technique is a method that is used to determine the concentration of a chemical compound or chemical element. There are a wide variety of techniques used for analysis, from simple weighing (gravimetric) to titrations (titrimetric)to very advanced techniques using and the software user interface.
Using empirically supplied current highway conditions, traffic forecasts, and established engineering relationships predicting the impact of highway condition on performance, HERS will identify deficiencies and simulate simulate - simulation highway improvements that could satisfy user objectives. These Hers-generated, system improvement sets are evaluated, and reports on initial improvement costs, user impacts, and physical conditions are provided.
Numerous alternatives are considered to correct each section deficiency and the economically "best" section improvement alternative is selected. These best improvements are then compared to find the best system solution. Alternatives are evaluated through comparison of the benefits and costs generated through simulated implementation of each option under consideration. This process tends to produce the most economically beneficial highway investment strategies.
Use of this technique has several implications: * User cost considerations a re key to improvement
selection decisions. In HERS, the question
is: "What impact does system condition
and performance have on highway users?"
rather than "What impact do highway users
have on system conditions and performance?" * Several potential improvement options for
any deficiency are identified and analyzed an·a·lyze
tr.v. an·a·lyzed, an·a·lyz·ing, an·a·lyz·es
1. To examine methodically by separating into parts and studying their interrelations.
2. Chemistry To make a chemical analysis of.
3. . * The economically "best" time to implement
an improvement is considered.
Software user interface
The software user interface is unique and allows for the straightforward development and analysis of policy scenarios. The model is accessible; it operates on a personal computer and is user-friendly. The analyst may readily control the following variables: * Deficiency levels: The user can adjust the deficiency
levels used in the HERS procedure to
target highway sections for potential improvement.
(See discussion of deficiency triggers,
below.) * Improvement selection criteria: The user controls
the benefit/cost thresholds, establishes
funding or system condition constraints CONSTRAINTS - A language for solving constraints using value inference.
["CONSTRAINTS: A Language for Expressing Almost-Hierarchical Descriptions", G.J. Sussman et al, Artif Intell 14(1):1-39 (Aug 1980)]. , assigns Individuals to whom property is, will, or may be transferred by conveyance, will, Descent and Distribution, or statute; assignees.
The term assigns is often found in deeds; for example, "heirs, administrators, and assigns to denote the assignable nature of
relative importance to the various user
benefits, and specifies user-cost objectives by
highway functional class or vehicle type
categories. * Input parameters: inputs such as improvement
costs and the discount rate are easily
modified by the user. * Analysis objective: The system will operate in
one of two modes: It will predict system conditions
and performance given varying funding
levels, or it will estimate the funding required
to achieve a user-specified level of
Interest in quantifying highway investment requirements--current and future--was established with the 1968 Congressional requirement for a biennial biennial, plant requiring two years to complete its life cycle, as distinguished from an annual or a perennial. In the first year a biennial usually produces a rosette of leaves (e.g., the cabbage) and a fleshy root, which acts as a food reserve over the winter. "Needs Report." The continuum in figure 1 summarizes the developmental history of highway investment analysis techniques.
The first Needs Report, in 1968, provided a summary of independently assessed State highway needs. The States reported the investment level required to correct all current and anticipated pavement pavement, the wearing surface of a road, street, or sidewalk. Parts of Babylon and Troy are believed to have been paved; Roman roads were noted for their durable stone paving. Cobblestones were common from late medieval times into the 19th cent. , alignment, and capacity deficiencies to the year 1985 ("full needs"). National standards for system classification, sufficiency rating criteria, or inventory data were not available. This first -era" was characterized char·ac·ter·ize
tr.v. character·ized, character·iz·ing, character·iz·es
1. To describe the qualities or peculiarities of: characterized the warden as ruthless.
2. by the perception of unlimited capital investment resources, and system expansion was the goal. (3)
By the early 1970's, the demand for highway travel was increasing dramatically, but investment resources were limited. The need to prioritize pri·or·i·tize
v. pri·or·i·tized, pri·or·i·tiz·ing, pri·or·i·tiz·es Usage Problem
To arrange or deal with in order of importance.
v.intr. capital improvement projects had become apparent.
The 1972 report benefitted significantly from improved data collection and analytical techniques. The 1970 National Highway Functional Classification and Needs Study provided standardized standardized
pertaining to data that have been submitted to standardization procedures.
standardized morbidity rate
see morbidity rate.
standardized mortality rate
see mortality rate. information on physical conditions and needs by functional class.
Further, the concept of minimum tolerable tol·er·a·ble
1. Capable of being tolerated; endurable.
2. Fairly good; passable. See Synonyms at average.
tol conditions (MTC mtc - A Modula-2 to C translator.
ftp://rusmv1.rus.uni-stuttgart.de/soft/Unixtools/compilerbau/mtc.tar.Z. ) was introduced. The MTC's represented a consensus of highway engineer expert opinion regarding highway safety, performance, and physical design. Each functional class was assigned an appropriate MTC level. For the first time, "needs" estimates represented the cost to provide a standard level of condition appropriate for a particular system's function (as opposed to jurisdiction).
The 1972 report included an assessment of investment priorities as well as an analysis of various alternatives to full needs. Relatively sophisticated modeling techniques were used to evaluate alternative investment options intended to "maintain (or preserve) the physical system." This report exhibited an important new orientation toward "system preservation" and marked the beginning of highway investment analysis as conducted today. (4)
In the mid-1970's, the notion of performance-related investment was taking hold as the appropriate way to express highway investment options given constrained con·strain
tr.v. con·strained, con·strain·ing, con·strains
1. To compel by physical, moral, or circumstantial force; oblige: felt constrained to object. See Synonyms at force.
2. funding. The 1976 National Highway Inventory and Performance Study (NHIPS) provided the data and analytical analytical, analytic
pertaining to or emanating from analysis.
control of confounding by analysis of the results of a trial or test. modeling techniques necessary to establish the foundation for designing a framework to evaluate the tradeoffs between capital investment and changes in highway system conditions and performance. (5)
The Highway Performance Monitoring System (HPMS HPMS Highway Performance Monitoring System
HPMS Harper Park Middle School
HPMS Hierarchical Process Modeling System
HPMS High Performance Mass Spectrometers
HPMS High Performance Monitoring System
HPMS Home Pain Management Systems, Inc. ) was introduced in the 1983 report. The HPMS was the product of a long-term research and development effort initiated by the Federal Highway Administration The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. The agency's major activities are grouped into two "programs," The Federal-aid Highway Program and the Federal Lands Highway (FHWA FHWA Federal Highway Administration (US DoT) ) to establish a continuous data collection system and develop analytical models to project future investment requirements based on the current state of the highway system. Although the coordinated HPMS data base and analytical package is highly regarded, it does not explicitly consider the relationship between user benefits and improvement costs. (6)
A shift from a primarily engineering orientation to one which includes economics, or user costs, characterizes the third era depicted de·pict
tr.v. de·pict·ed, de·pict·ing, de·picts
1. To represent in a picture or sculpture.
2. To represent in words; describe. See Synonyms at represent. on the continuum. The user impact orientation of HERS allows decision makers to compare productivity, or return on investment, for various scenarios.
The next mark on the continuum is expected to be the expansion of HERS from an exclusively highway investment analysis tool to one that includes options for alternative surface transportation system improvements. The benefit/cost framework of HERS can accommodate the inclusion of multimodal Two or more modes of operation. The term is used to refer to a myriad of functions and conditions in which two or more different methods, processes or forms of delivery are used. On the Web, it refers to asking for something one way and receiving the answer another; for example requesting improvement options. The first step in this HERS evolution is to incorporate transit options.
Relationship of HERS to HPMS
HPMS system overview
A flowchart of the HPMS analytical procedure is presented in figure 2. As with HERS, the model predicts resulting highway conditions, identifies deficiencies, and selects potential improvements to correct the deficiencies based on user-specified travel demand.
However, when the HPMS model identifies a deficiency and it simulates the improvement selection decision process, only one pre-determined improvement is selected for each deficiency. Cost-effectiveness is not considered.
The HPMS model can also test the impact of constrained system investment. The improvement selection decision process is extended to include prioritization of the individual improvements necessary to correct all deficiencies. The prioritization procedure is primarily a function of changes to physical conditions as opposed to user cost impacts.
The HPMS uses a cost effectiveness index to measure system performance and determine decisions given constrained funding objective. It is derived from the status of physical characteristics (pavement, alignment, etc.). Although it is understood that user costs vary with physical conditions, they are not directly calculated.
Use of HPMS in HERS development
Development of HERS assumed that the HPMS data base would be used and that many of the procedures from the HPMS analytical models would be shared as well. The contract to develop HERS did not include provisions for developing new engineering relationships or collecting additional highway inventory data.
The comprehensive HPMS data base is the most detailed description of the Nation's highway conditions available. It is a stratified stratified /strat·i·fied/ (strat´i-fid) formed or arranged in layers.
Arranged in the form of layers or strata. random sample of approximately 105,000 sections of non-local roads. The data base is updated annually.
The HPMS analytical procedures Analytical Procedures is one of financial audit skill which help an auditor understand the client's business and changes in the business, to identify potential risk areas and to plan other audit procedures. have been extensively reviewed by government oversight
Oversight may refer to:
However, the unique features of HERS--its deficiency identification and improvement selection process, its extraordinary computation Computation is a general term for any type of information processing that can be represented mathematically. This includes phenomena ranging from simple calculations to human thinking. requirements, and its increased sensitivity to user costs-- necessitated significant modifications to the HPMS procedures.
In fact, the forecasting procedure was the only HPMS process applied directly to HERS. It should be noted, however, that even when the HPMS procedures were modified, the underlying engineering relationships were preserved.
HERS system description
The HERS system will run on a 386-class microcomputer microcomputer
Small digital computers whose CPU is contained on a single integrated semiconductor chip. As large-scale and then very large-scale integration (VLSI) have progressively increased the number of transistors that can be placed on one chip, the processing capacity . The main HERS program has 74 subroutines and 425,000 bytes of source code and is written primarily in standard FORTRAN 77.
HERS system overview
A schematic A graphical representation of a system. It often refers to electronic circuits on a printed circuit board or in an integrated circuit (chip). See logic gate and HDL. overview of the HERS procedure is presented in figure 3. The user first defines a policy scenario for analysis. For example, the user may be interested in system user-cost levels resulting from a constrained highway investment budget. By changing the parameters in the HERS "RUNSPEC" file, the user indicates the level of available investment, acceptable values for project benefit/cost ratios, levels at which a section will be found deficient de·fi·cient
1. Lacking an essential quality or element.
2. Inadequate in amount or degree; insufficient.
a state of being in deficit. , and so on.
The user also determines the length of the overall analysis period (OAP OAP - Outside Awareness Port ) and the length of the funding periods. Generally, the highway system will be evaluated over a 20-year horizon (OAP) divided into four funding periods of 5 years each. HERS will implement no more than one improvement type per deficient highway section for each funding period.
The HERS analysis process starts by forecasting traffic growth and pavement condition for each highway section in the HPMS data base. The model then proceeds to the first pass where it evaluates each section for unacceptable conditions. Unacceptable conditions refer to deficiencies that the user determines must be corrected regardless of economic attractiveness. A potential least-cost improvement is identified to correct each deficiency.
User benefits and costs associated with the least-cost improvement are simulated and used to generate an incremental benefit/cost ratio (IBCR IBCR Influence-Based Channel Reservation ). The selected improvements are then prioritized according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. their IBCR. Depending on the user-defined constraints (e.g., available funding), these improvements are placed on a list for potential selection.
A deficiency that violates the unacceptable conditions standard will always be improved. However, each potential improvement selected in the first pass will be re-evaluated in the second pass to consider the economic feasibility of implementing a higher cost, more aggressive option.
In the second pass, highway sections violating the user-defined "serious deficiency level" or "deficiency level" are evaluated. All potential improvements are identified and considered for implementation via the incremental benefit/cost procedure. Improvements are selected according to their IBCR's until some user defined constraint Constraint
A restriction on the natural degrees of freedom of a system. If n and m are the numbers of the natural and actual degrees of freedom, the difference n - m is the number of constraints. is violated vi·o·late
tr.v. vi·o·lat·ed, vi·o·lat·ing, vi·o·lates
1. To break or disregard (a law or promise, for example).
2. To assault (a person) sexually.
3. . The best improvements are simulated, and final reports are produced. The unique features of HERS are described in greater detail below.
HERS checks eight characteristics of each highway section for deficiencies: pavement condition, surface type, volume/capacity (V/C V/C Volume/Capacity
V/C Variants/Configurations ), lane width, right shoulder width, shoulder type, horizontal alignment, and vertical alignment.
There are three levels of deficiencies within the HERS framework: unacceptable level, serious deficiency level and deficiency level. These deficiency triggers serve two important functions.
First, they allow the user to control computation time In computational complexity theory, computation time is a measure of how many steps are used by some abstract machine in a particular computation. For any given model of abstract machine, the computation time used by that abstract machine is a computational resource which can be . HERS currently requires well in excess of 1 working day to evaluate a scenario using the full sample set. The 'run time" may be reduced, without losing significant accuracy, by judiciously ju·di·cious
Having or exhibiting sound judgment; prudent.
[From French judicieux, from Latin i setting the deficiency levels.
Second, they allow the user to establish the allowable condition of a section. There is a lack of consensus concerning how the MTC's should be established. For example, it has been suggested in policy debate that the MTC for congestion The condition of a network when there is not enough bandwidth to support the current traffic load.
congestion - When the offered load of a data communication path exceeds the capacity. should be lowered from a level of service "D" to "E" or "F." The impact of such a policy change can be readily tested using HERS.
Highways violating the "unacceptable level" standard will always be corrected (assuming available funds) with, at least, an inexpensive improvement. There is no requirement for these improvements to pass the benefit/cost test.
Serious deficiency level (SDL (Specification and Description Language) A modeling language used to describe real time systems. It is widely used to model state machines in the telecommunications, aviation, automotive and medical industries. ) standards are used to reduce the number of improvements analyzed to correct a deficiency, reducing the HERS run time. If the SDL for a given section characteristic is violated, only one improvement that corrects the SDL deficiency will be considered.
The HERS model will analyze up to six aggressive and nonaggressive improvement options for any section violating a user-defined deficiency level (DL). The greater the number of potential improvements evaluated, the closer the final set of system improvements will be to optimal.
The closer a deficiency trigger is set to the MTC, the fewer the number of potential improvements that will be analyzed (decreases computation time). The closer the trigger is to the design standard, the larger the number of potential improvements that will be analyzed.
Improvement options and costs,
Improvement types considered by HERS consist of various combinations of pavement, widening, and alignment options. The HERS model selects from among 28 improvement types. The options range from least aggressive (e.g., resurfacing) to more aggressive (e.g., reconstruct re·con·struct
tr.v. re·con·struct·ed, re·con·struct·ing, re·con·structs
1. To construct again; rebuild.
2. with improved alignment).
Life-cycle incremental benefit/cost analysis: An overview
HERS uses benefit/cost analysis (BCA BCA Business Case Analysis
BCA Building Code of Australia
BCA Boeing Commercial Airplanes
BCA Board of Contract Appeals
BCA Boston Center for the Arts
BCA Billiard Congress of America
BCA Bureau of Criminal Apprehension
BCA Breast Cancer Action ) to select the best improvement options for each user-defined funding period. The heart and soul of the BCA procedure is the benefit/cost ratio (BCR BCR B Cell Receptor
BCR Business Communications Review (magazine)
BCR Banca Comerciala Romana (Romanian bank)
BCR Breakpoint Cluster Region
BCR Benefit/Cost Ratio
BCR Bay City Rollers ):
User Costs + Agency Costs Agency Costs
The costs resulting from an agent performing services for a principal.
Agency costs are generally the commissions earned by agents.
See also: Agency Problem, Agent, Principal
Agency costs + Residual Value/Improvement Cost
For each improvement option, user costs and ongoing agency maintenance costs are calculated. Also calculated is the amount by which implementing this improvement will reduce the cost of subsequent improvements (residual value). Improvement cost refers to the initial cost of the improvement.
The IBCR is calculated by comparing the BCR (or IBCR) from one improvement option to the BCR (or IBCR) associated with another base case alternative. The BCR, as used in HERS, is expressed in "present value." That is, it represents the stream of benefits and costs over the overall analysis period, discounted back to the funding period of interest.
The key concept underlying BCA is the sequential comparison of alternative options until the "optimal" action is found. HERS evaluates alternative options in three dimensions: 1. Alternatives are compared to the option of
postponing any improvement to address the
deficiency until a subsequent funding period.
The question addressed in the first dimension
is: "Should the deficiency be corrected now
or later?" 2. Assuming that the above analysis finds addressing
the deficiency in the current funding
period to be economically acceptable, HERS
proceeds to the second dimension. The option
with the highest IBCR relative to the
tr.v. post·poned, post·pon·ing, post·pones
1. To delay until a future time; put off. See Synonyms at defer1.
2. To place after in importance; subordinate. any improvement option" is compared
to more aggressive alternatives that
could correct the deficiency. This is done in a
sequential fashion until the improvement with
the highest IBCR is identified. The question
addressed in the second dimension is: "What
is the best improvement to correct this section
deficiency?" 3. After all HPMS highway sections have passed
through the first two dimensions of analysis,
improvements are selected in order of IBCR
for system implementation until some user-defined
scenario constraint has been violated
(e.g., funds are exhausted). The question addressed
in the third dimension is: "Given the
user- defined system constraint, what mix of
improvements will generate the highest return
on the investment dollar?"
A detailed flowchart of the HERS benefit/cost and improvement selection procedures is presented in figure 4.
The HERS model represents a significant advancement in the methodology available to estimate National level highway investment requirements. Results from this model will provide a "highway-user dimension" to needs analysis.
The system is designed to readily accommodate necessary refinements as new research findings become available. It is anticipated that future versions of HERS will include an expanded list of improvement options (e.g, new construction on new alignment, demand management strategies, and other-mode options), additional benefits (e.g., National economic impacts), and additional costs (e.g., air and noise pollution).
Throughout the HERS development process, one of the more important goals was to produce a working model that would use the best data and highway engineering knowledge available. To facilitate this process, the contractor designed HERS using an open framework, or modular, structure. The model is viewed as a work in progress" with the FHWA's intent being to update and refine HERS as the results of various research efforts become available. (1) Italic number in parentheses See parenthesis.
parentheses - See left parenthesis, right parenthesis. identify references on page 111.
(1) U.S. Congress, House, Committee on Public Works and Transportation, The Status of the Nation's Highways and Bridges: Conditions and Performance Report of the Secretary of Transportation, House Document No. 101-2, 101st Congress, 1st Session, Washington, DC, June 1989, p. 2. (2) The Highway Economic Requirements System (HERS): Users Guide, Technical Report and System Maintenance Manual, documentation produced in three parts under FHWA Contract DTFH61-88-C-00006 by Jack Faucett Associates, Bethesda, Maryland Bethesda is an urbanized, but unincorporated, area in southern Montgomery County, Maryland, just Northwest of Washington, D.C. It takes its name from a church located there, the Bethesda Presbyterian Church, built in 1820 and rebuilt in 1850, which in turn took its name from , July 1991. (Available from the Office of Policy Development [HPP-22], Federal Highway Administration, Washington, DC) (3) U.S. Congress, House, Committee on Public Works, 1968 National Highway Needs Report, transmitted by the Secretary of the Department of Transportation, House Document No. 91-28, 90th Congress, 2d Session, Washington, DC, 1968. (4) U.S. Congress, House, Committee on Public Works, Part I of the 1972 National Highway Needs Report, transmitted by the Secretary of the Department of Transportation, House Document No. 92-266, 92d Congress, 2d Session, Washington, DC, March 1972. (5) U.S. Congress, House, Committee on Public Works, The Status of the Nation's Highways: Conditions and Performance Report of the Secretary of Transportation, House Document No. 95-29, 95th Congress, 1st Session, Washington, DC, September 1977. (6) U.S. Congress, House, Committee on Public Works and Transportation, The Status of the Nation's Highways: Conditions and Performance Report of the Secretary of Transportation, House Document No. 98-14, 98th Congress, 1st Session, Washington, DC, July 1983.
Regina McElroy is a transportation specialist in Federal Highway Administration's (FHWA's) Highway Needs and Investment Branch in the Office of Policy Development. She is responsible for development and implementation of the Highway Economic Requirement System (HERS) model. Before joining the FHWA, Ms. McElroy was an economist with the American Trucking Associations, Inc.