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OCR for page 59
Benefit-Cost Analysis 59
4.1 Benefit-Cost Analysis Approach
As noted in the previous section, a B-C analysis would have allowed for the assessment of the
relative importance of different types of benefits for any given scenario/alternative for truck-only
lane application. It also would have allowed for a determination of which configurations appear
to deliver the highest level of net benefits after taking costs into account. This is particularly
important when comparing LCV versus non-LCV operations on truck-only lanes since costs
may be higher for LCV systems off-setting some of the productivity benefits. Yet, most of the
studies reviewed for the performance evaluation task did little to assess the cost-effectiveness of
truck-only lanes compared to other alternatives (such as additional mixed-flow lanes) based on
the development of B-C ratios. Due to this constraint, alternative approaches were developed for
the B-C analysis in this study.
The approach that was taken in this study was to define a representative baseline (generic) cor-
ridor for each of the two scenarios/corridor types (long-haul intercity and urban), to apply the
approaches and data provided by the previously reviewed studies, use standard values from the
literature to monetize benefits, and use data from the prior studies to estimate costs. The B-C
analysis was based on a net present value (NPV) analysis approach, which is described below.
4.1.1 Net Present Value Analysis
The B-C analysis was based on an NPV analysis approach using a base year of 2008 and a time
horizon of 2030 for the analysis. Monetized benefits and costs were estimated for each year
in the 2008 through 2030 time period and discounted to the base year (2008) to get the NPV of
B-C ratios for each alternative. Benefits were calculated for a similar set of performance measures
as those evaluated in the reviewed studies. The benefits were monetized using monetary values
for travel times and reliability (using auto and truck value of time estimates) and monetary val-
ues for accidents (by type of accident). Costs were calculated based on unit cost factors devel-
oped from the literature (a detailed discussion of the benefit monetization factors and unit costs
is presented in Appendix C, which is available on the TRB website at www.TRB.org by search-
ing for NCHRP Report 649/NCFRP Report 3, and summarized later in this chapter). A later sec-
tion describes the traffic growth and other economic assumptions used for the NPV analysis.
As described earlier, representative baseline corridors were defined for the B-C analysis, so
that the relative benefits-costs of truck-only lanes in different corridor applications could be eval-
uated. The following section describes the corridor concepts defined for the B-C analysis.
4.1.2 Representative Baseline Corridors
The representative baseline corridors defined for the B-C analysis are not actual corridors but
are generic corridors, that provided us with the opportunity to control characteristics of the cor-
ridors for analysis purposes. Although not actual corridors, the characteristics (e.g., auto and
truck traffic volumes, length of corridor, and number of lanes) are derived from actual corridors
evaluated for truck-only lanes throughout the country. Readers should view the B-C ratios calcu-
lated with this approach with some caution as they are not based on detailed analysis using data from
actual corridors. However, for comparative purposes, and to give an idea of the range of assump-
tions that would make truck-only lanes a preferred alternative, the approach is useful.
For each baseline corridor scenario (long-haul and urban), a set of general corridor and traffic
characteristics were defined. These characteristics included the following:
· Length of corridor,
· Number of lanes and capacity, and
· Total average daily traffic (ADT) and heavy-truck ADT.
OCR for page 60
60 Separation of Vehicles--CMV-Only Lanes
For each baseline corridor scenario, a set of meaningful alternatives was defined including a
truck-only lane alternative (which included two operational scenarios--with and without LCVs--
in the case of a long-haul corridor), a mixed-flow lane alternative (to assess the relative benefits
and costs of truck-only lanes compared to additional mixed-flow lanes), and a no-build alternative.
Subsequent sections provide a more detailed description of the alternatives considered within
each corridor scenario.
Because the data inputs for the B-C analysis for the urban and long-haul corridor scenarios
have a high degree of uncertainty associated with them (such as costs and factors impacting truck
diversion rates), and the magnitude of this uncertainty is unknown, the study team felt uncom-
fortable computing a single B-C ratio for each alternative. In order to recognize uncertainty in
key input variables, a sensitivity analysis approach was used for the B-C analysis, which is
described below.
4.1.3 Sensitivity Analysis Approach
To capture some of the uncertainties involved in the range of factors driving the diversion of
truck traffic to truck-only lanes (which have a direct impact on the performance benefits estimates
of truck lanes), as well as the uncertainties in capturing the range of costs for truck-only lane proj-
ects, a sensitivity analysis approach was used for the B-C analysis. A key variable in the analysis is
the assumption about how much truck traffic diverts to the truck-only lanes. In the case of truck-
only lanes without LCV operations, diversion rates should be a function of the relative congestion
conditions on the mixed-flow lanes (assuming trucks are not required to operate on the truck-only
lanes), number and placement of the exits and entrances to the truck-only lanes (and an associated
cost tradeoff), and the O-D patterns of the trucks. In the case of truck-only lanes with LCV oper-
ations, diversion rates are expected to be a function of the connectivity to a larger LCV network,
commodities carried (not all commodities will benefit from LCV operations), O-D patterns of the
trucks, and off-system infrastructure availability (staging areas) and costs of LCV operations. None
of the performance evaluations of LCV operations described in the previous chapter have con-
ducted this type of thorough evaluation of the LCV market opportunities and they have tended to
assume very high levels of trucks diverting to LCVs. However, analysis conducted for the I-15 Com-
prehensive Corridor Study in Southern California and analysis underway at the time of this study of
potential LCV operations in the I-80/90 corridor between Chicago and Boston conducted for
FHWA suggest that the markets for LCV operations in real corridors might be considerably
smaller than previous studies have assumed. Therefore, the sensitivity analysis involved consider-
ing a range of diversion rates and assessing the impact of diversion rates on B-C ratios. The sensi-
tivity analysis also considers the uncertainty in cost estimates and varies these in order to take into
account potentially missing cost elements or certain widely varying unit cost factors reported in
the literature.
For long-haul corridors, the sensitivity analyses included the following:
· Variations in rates of diversion to LCV lanes and truck-only lanes without LCVs, and
· Variations in costs.
For urban corridors the sensitivity analyses included the following:
· Variations in rates of diversion to truck-only lanes, and
· Variations in costs.
The sensitivity analysis approach for the B-C analysis of truck-only lanes along long-haul and
urban corridors is useful in gaining the following key insights:
· Assessing the range of diversion rates that would result in truck-only lanes being cost-effective
in comparison to adding mixed-flow capacity;
