StratBENCOST was developed by NCHRP project 2-18(4) as a tool to evaluate highway investments at the strategic level. The model embodies relationships derived from MicroBENCOST and HERS, both of which address benefit-cost assessment in greater detail than this model. Nevertheless, StratBENCOST offers a sophisticated benefit-cost analysis with nearly the same amount of input data and use of default cost and performance parameters as the other more advanced evaluation tools. The software is also known as RAP32 — Risk Analysis Process 32 — highlighting the fact that it explicitly quantifies uncertainty in input parameters, using a Monte Carlo simulation methodology.
StratBENCOST distinguishes between two situations: (1) a single road-segment where proposed improvements have no significant traffic diversion consequences, and (2) a proposed highway investment in a network with significant diversion. In the later case, the program requires a level of traffic input suggesting the need for inputs from a regional 4-step travel demand model.
Project Types Evaluated: For each of the basic modeling approaches (either single highway segment or improvement within a network), the program can manage data for up to 20 investment alternatives, which are called "scenarios." Each scenario represents a particular investment alternative being evaluated relative to a base case. The program may be used to compare a proposed investment to a "do nothing" zero-cost option or to compare two alternative levels of investment, in which the base case would normally be the less costly of the two. In single segment modeling, scenarios may incorporate combinations of pavement treatments (including pavement maintenance measures), capacity enhancements, grade changes, facility type changes (converting to 2 & 3-lane, multilane undivided or divided), and changes in access control (freeway, expressway, or otherwise). In network modeling, the comparison considers only the traffic consequences of two future network investment alternatives, with the specific nature of the network improvements, whether physical or operational changes, addressed externally, usually in the 4-step demand modeling process, not in StratBENCOST. The program contains a library of partially defined default scenario types that the user can build upon to generate customized investment scenarios.
Scope of Application: Benefits and costs are analyzed for a user-specified evaluation period up to 30 years. Benefits begin to flow following a user-specified time interval needed to implement the project alternative (typically the duration of construction). Cost estimates for different components of cost are specified year-by-year throughout the evaluation period. In the case of single highway segment analysis, benefits are based on the annual average daily traffic (AADT), which is assumed to grow at a constant rate throughout the evaluation period. Induced traffic may be estimated for the project alternative using a demand elasticity applied to differences in total travel costs. Travel cost savings are assumed to apply fully to any induced traffic, not as suggested by consumer surplus theory. The facility AADT in each year is factored to provide peak and off-peak shares, and to provide volumes for three different vehicle types: autos, trucks, and buses. In the case of network modeling, benefits are based on separate traffic estimates input for the base case and the project alternative, for different highway types in the network (freeways, expressways, major arterials, minor arterials, and collectors). For each highway type in the network, the user must input total mileage, daily vehicle-miles traveled (VMT), and daily vehicle-hours-traveled (VHT).
A noteworthy aspect of StratBENCOST is how it incorporates risk in each analysis. Virtually every input variable can be specified as a random variable, by inputting its median, 10%ile, and 90%ile values. Corresponding probability distributions are generated, along with other related parameters such as mean and standard deviation. When the benefit-cost calculations are done, values of inputs are randomly generated from these distributions through a series of Monte Carlo trials, and results are given in the form of probability distributions, with their related parameters.
Benefit Categories Considered:
Cost Categories Considered:
Economic Performance Measures for Each Alternative, Compared to the Base Case:
Note that in the version of StratBENCOST_32 tested, the benefit-cost ratio is calculated by dividing the sum of the changes in the benefits listed above by the sum of capital, right-of-way, and "other" project costs. The maintenance and life cycle costs are omitted from the calculation, as well as from the IRR calculation. The total benefits are calculated as the sum of the benefits listed above plus changes in maintenance and life cycle costs. The net benefit calculation, as expected, provides the sum of all benefits and costs.
Available results include the different components of costs and benefits, aggregated over the evaluation period. Intermediate results (e.g. numbers of collisions, emission quantities, annual costs and benefits) are not provided.
StratBENCOST is distributed by HLB Decision Economics Inc., the company that developed it (http://www.hdrinc.com/15/14/default.aspx), and by McTrans (http://mctrans.ce.ufl.edu/), where the software and documentation are available for under $75. Documentation includes the user manual (HLB Inc., 1999) as well as an introduction to the program (NCHRP-a), a technical description (NCHRP-b), and a tutorial (NCHRP-c), all of which are contained on the distribution CD.
A tutorial that accompanies the program provides example StratBENCOST applications based on evaluations performed for the Arizona Dept. of Transportation. One is a single-segment analysis that addresses whether it is economically justified to upgrade a congested two-lane rural highway, 28.8 miles long, to create a partial-access-controlled four-lane facility. It was assumed that traffic levels would not be affected by the upgrade, therefore a zero value of elasticity was used. 1996 was used as the base year, and it was assumed that the highway would be resurfaced in year 3 (1999) if widened, and in year 18 (2014) if not. Most of the key input data are shown in the table below. Note that most inputs are specified as random variables by giving their cumulative distributions. For example, the time to implement the improvement (project duration) ranges from 2.5 to 4 years with a 50/50 likelihood of taking 3 years.
Cost, travel time and delay, accident, and emission relationships built into the model were used to estimate the components of benefits incurred during a 20-year analysis period. After being discounted at 7%, the principal results from the program are the following:
The calculations, based on 500 Monte Carlo trials, show that the proposed upgrade provides an excellent economic payoff, with about $300 million in expected net benefits. The table shows the average and median, as well as the 10%ile and 90%ile values for each output. Also available are other %ile values and additional statistics describing each distribution. Several distribution graphs can be generated, such as one for net benefits.
In this example, when risk is considered, net benefits and other economic indicators are overwhelmingly positive. There exists only a 10% probability that the net benefits (net present worth) are below about $190 million.
Although having much in common, the single-segment and network models within MicroBENCOST have a few major differences, as summarized in the table below:
Except for very simple networks, the inputs over time of vehicle-miles-traveled (VMT) and vehicle-hours-traveled (VHT) by highway type for a network analysis would normally be developed using an external travel demand model, where effects of peak/off-peak and, in theory, pavement conditions can be considered.
Vehicle operating cost calculations in the single-segment model consider speed, grade, speed cycles and pavement condition, producing resource consumption by vehicle type for fuel, oil, tires, vehicle maintenance, and vehicle depreciation. Additional increments of resource consumption are calculated based on speed cycles, which reflect volume-capacity ratios and pavement conditions. All default estimates are based on data from an earlier NCHRP study. (Texas Transportation Institute, 1990) Resource consumption is converted to costs using year-one unit prices and real price indices for each year in the analysis period.
StratBENCOST incorporates a fairly simple, conservative travel time and delay estimation logic based on a family of speed v. volume-capacity relationships, representing seven urban and five rural highway types. Capacities of the different facility types are based on the 1985 Highway Capacity Manual. Possible delays due to queuing are not considered.
Accident benefits are estimated by the program using built-in tables of accident rates stratified by highway type and AADT level, differentiated as to fatalities, injuries, and property damage collisions, with default data from a 1991 FHWA study. (Jack Faucett Associated, 1991). Default unit costs of accidents are from a 1991 Urban Institute study. (Miller et al, 1991)
Emissions benefits are estimated based on VMT traveled at each speed, using a built-in table of average emission factors developed by a 1982 FHWA study. (Texas Research and Development Foundation, 1982) Default unit cost values for carbon monoxide (CO), hydrocarbons (HC), and nitrous oxides (NOx) are from a more recent TRB paper. (Wang & Santini, 1995)
The program incorporates a large library of default unit costs and other parameter values that can be modified as desired by the user. The methodology is described in detail in the Model Structure Report. (NCHRP-b)
Transportation Research Board. Development and Demonstration of StratBENCOST Procedure. National Cooperative Highway Research Program Research Results Digest 252 (NCHRP RRD 252). Washington DC. March 2001. Available at: http://gulliver.trb.org/publications/nchrp/nchrp_rrd_252.pdf. Accessed April 2004.
Hickling Lewis Brod (HLB) Inc. User's Manual for StratBENCOST32. National Cooperative Highway Research Program — NCHRP 2-18(4). Transportation Research Board. Washinton DC. August 20, 1999.
National Cooperative Highway Research Program (NCHRP-a). Introduction To StratBENCOST — Strategic Decision Support Tool for Highway Planning and Budgeting. NCHRP Project 2-18(4). Transportation Research Board. Washington DC.
National Cooperative Highway Research Program (NCHRP-b). User-Cost Synthesis And Model Structure For StratBENCOST — Strategic Decision Support Tool for Highway Planning and Budgeting. NCHRP Project 2-18(4). Transportation Research Board. Washington DC.
National Cooperative Highway Research Program (NCHRP-c). Tutorials And Ready-Reckoner For StratBENCOST — Strategic Decision Support Tool for Highway Planning and Budgeting. NCHRP Project 2-18(4). Transportation Research Board. Washington DC.
Texas Transportation Institute. Technical Memorandum for National Cooperative Highway Research Program (NCHRP) Project 7-12. The Texas A&M University System, College Station, Texas, January 1990.
Texas Research and Development Foundation. Vehicle Operating Costs, Fuel Consumption, and Pavement Type and Condition Factors. Austin, Texas. Federal Highway Administration. June 1982.
Wang, M. and D. Santini. Monetary Values of Air Pollution Emissions in Various U.S. Areas. Transportation Research Board. Annual Meeting. Paper 951046. January 1995.
Jack Faucett Associates. Highway Economic Requirements System Technical Report. Bethesda, MD. Report for the Federal Highway Administration, U.S. DOT. Washington, DC. July 1991.
Miller, T., J. Viner, N. Pindus, et al. The Cost of Highway Crashes. The Urban Institute. Report for the Federal Highway Administration, U.S. DOT. Washington DC. 1991