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70 Separation of Vehicles--CMV-Only Lanes
NPV of safety benefits. The estimation of NPV of safety benefits associated with the build
alternatives was developed by calculating accident rates per million VMT as a function of V/C
using look-up factors from the previously mentioned IDAS handbook. These were further
reduced by 15% for the truck-only lanes to account for the benefits of truck-auto separations
based on the results of previously cited research by Douglas. A more complete description of this
approach is included in Appendix C.
4.7 Results of the Benefit-Cost Analysis
4.7.1 Long-Haul Corridor
In order to develop the B-C analysis of a generic corridor, a number of assumptions about key
variables needed to be made. In analysis of an actual corridor, these need not be assumptions but
could be based on market analysis of actual conditions. Further, without taking into considera-
tion actual corridor conditions, the need for interchanges, and the need for supporting infra-
structure (like staging areas), cost estimates for the long-haul corridor alternatives could vary
widely from the assumptions used in the generic corridor analysis.
Costs
This section presents the comparative costs for all cost components of each alternative. The
cost estimates are developed using the unit costs presented in an earlier section, and the config-
urational and travel demand characteristics along the generic corridor. Since there is inadequate
information on some of the truck-only lane cost components such as O&M costs and LCV
equipment costs, the B-C analysis uses a range of costs. The range of costs was developed by first
estimating a baseline total cost for each alternative, and varying the costs across the baseline
(lower and upper limit costs with the baseline as the mean) using a variance of ±20% relative to
the baseline.
Table 4.4 presents the baseline cost components for each of the alternatives. A detailed discus-
sion of the approach to calculating costs and their relationship to the NPV analysis is presented
in Appendix C.
As mentioned previously, to account for the uncertainty in costs in the sensitivity analysis, the
total costs for each alternative in Table 4.4 are varied to arrive at a representative range of cost
estimates for the B-C analysis. Table 4.5 presents these cost variations for the long-haul corridor
alternatives.
Table 4.4. Baseline cost components for long-haul corridor alternatives,
in billions of dollars (indexed to 2008).
Truck-Only Lanes
Additional Without LCV With LCV
Costs Mixed-Flow Lanes Operations Operations
ROW Acquisition 0.2 0.2 0.2
Construction (Lanes) 4.5 8.8 9.4
Construction (Interchanges) 0.7 0.7 0.8
Construction (Staging Areas--Rural
0.003
Locations)
Construction (Staging Areas--Urban
0.009
Locations)
O&M 0.4 0.8 0.8
Total 5.8 10.5 11.2
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Benefit-Cost Analysis 71
Table 4.5. Range of costs considered for the B-C analysis, in billions of dollars
(indexed to 2008).
Lower Limit for Cost Baseline Upper Limit for Cost
Alternative (20% Below Baseline) Cost (20% Above Baseline)
Additional Mixed-Flow Lanes 4.7 5.8 7.0
Truck-Only Lanes without LCV Operations 8.4 10.5 12.6
Truck-Only Lanes with LCV Operations 9.0 11.2 13.5
Monetized Benefits
As mentioned, a range of diversion rates is considered in the B-C analysis to assess the impact
of diversion rates on the performance benefits of truck-only lanes and to identify the range of
diversion rates for which truck-only lanes are observed to be cost-effective compared to adding
mixed-flow capacity. The results for the monetized benefits under each performance measure
for each alternative under different diversion rate assumptions are presented in Table 4.6. Note
that the results for the additional mixed-flow lane alternative do not change under different
diversion rate scenarios because they are only applicable to the truck-only lane alternative.
Benefit-Cost Results
Figure 4.1 shows the comparison of B-C results for each alternative as a function of diversion rates.
Conclusions
The following are key conclusions from the B-C analysis of truck-only lanes in the long-haul
generic corridor:
· The results suggest that high levels of diversion would be needed for truck-only lanes to be
judged a preferred alternative both in terms of getting to a B-C ratio greater than 1.0 and
exceeding the B-C ratio of adding more general purpose lanes.
· In the case of truck-only lanes without LCV operations, even under the most optimistic scenario
favoring this alternative (i.e., truck-only lane costs being closer to the lower threshold--20%
below the baseline; and additional mixed-flow lane costs falling in the upper threshold--20%
above the baseline), a minimum of 50% diversion would be required before the truck-only lanes
become more cost-effective compared to adding mixed-flow capacity. Under the applicability
Table 4.6. Monetized benefits of alternatives for different diversion rate assumptions,
in millions of dollars (indexed to 2008).
Additional Mixed-Flow Lanes Truck-Only Lanes without LCVs Truck-Only Lanes with LCVs
Diversion Travel Travel Travel
Rate (%) Productivity Time Safety Total Productivity Time Safety Total Productivity Time Safety Total
10 4.9 4.9 0.6 0.6 0.1 1.4 1.3 0.6 0.3 2.2
20 4.9 4.9 1.2 1.1 0.3 2.6 2.6 1.1 0.5 4.2
30 4.9 4.9 1.8 1.6 0.4 3.8 3.8 1.6 0.8 6.2
40 4.9 4.9 2.4 1.9 0.5 4.9 5.1 1.9 1.1 8.1
50 4.9 4.9 3.0 2.2 0.7 5.9 6.4 2.2 1.3 9.9
60 4.9 4.9 3.6 2.4 0.8 6.8 7.7 2.4 1.6 11.7
70 4.9 4.9 4.2 2.6 0.9 7.7 9.0 2.6 1.8 13.3
80 4.9 4.9 4.8 2.7 1.0 8.5 10.2 2.7 2.0 15.0
90 4.9 4.9 5.4 2.8 1.1 9.2 11.5 2.8 2.3 16.5
100 4.9 4.9 5.9 2.8 1.2 9.9 12.8 2.8 2.5 18.0
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72 Separation of Vehicles--CMV-Only Lanes
2.0
1.8
1.6
1.4
1.2
B/C 1.0
0.8
0.6
0.4
0.2
-
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Diversion Rate
Mixed Flow Upper B/C Limit Mixed Flow Baseline B/C Mixed Flow Lower B/C Limit
Truck Lane (w/o LCV) Upper B/C Limit Truck lane (w/o LCV) Baseline B/C Truck Lane (w/o LCV) Lower B/C Limit
Truck Lane (w/ LCV) Upper B/C Limit Truck Lane (w/ LCV) Baseline B/C Truck Lane (w/ LCV) Lower B/C Limit
Figure 4.1. B-C ratios for alternatives as a function of diversion rate.
of baseline conditions, the diversion rates would need to be very high (more than 85%) before
this alternative performs better in terms of cost-effectiveness compared to adding mixed-flow
lanes. Given this high level of diversion, which might not be achievable along long-haul cor-
ridors, particularly those with relatively lower levels of congestion, truck-only lanes without
LCV operations would generally appear to be an inappropriate choice under the general con-
ditions described for long-haul corridors.
· In the case of LCV operations on truck-only lanes, even under the most optimistic scenario
favoring this alternative (i.e., lower end of the costs for truck-only lanes and upper end of the
costs for mixed-flow lanes), a minimum of 30% diversion would be required before the truck-
only lane alternative becomes more cost-effective compared to adding mixed-flow capacity.
Under the applicability of baseline conditions, the diversion rate would need to be at least 50%
before truck-only lanes with LCV operations perform better compared to mixed-flow lanes.
Also, diversion to the LCVs would need to be in the range of 45% to 70% (depending on costs)
to achieve B-C ratios greater than 1.0.
· Based on the results, it appears that for long-haul corridors, the decision making for corridor
investment options would primarily be governed by the relative B-C performance of truck-
only lanes with LCV operations compared to additional mixed-flow lanes. If the market for
LCVs is not present along a corridor or is such that it would only result in lower diversion rates
(less than 30% based on Figure 4.1) based on the type of commodities, connectivity of the cor-
ridor to the larger LCV network, and/or truck O-D patterns, it would clearly rule out the appli-
cability of truck-only lanes along the corridor (given that typical conditions along long-haul
corridors would make truck-only lanes without LCVs not a preferred alternative compared to
adding mixed-flow lanes). Based on the market conditions, which would govern the potential
rate of diversion, the results from Figure 4.1 could be applied to assess the cost-effectiveness
of implementing truck-only lanes with LCV operations compared to adding mixed-flow
capacity along a corridor.
· As mentioned earlier, the results in Figure 4.1 are generated based on the defined characteris-
tics of the representative baseline corridor. Consequently, these trends are expected to change
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Benefit-Cost Analysis 73
based on changes in corridor congestion characteristics, which are not reflected in the results.
It is expected that these changes will be more pronounced for the mixed-flow lane and truck-
only lane without LCV alternatives (compared to the truck-only lane with LCV operation
alternatives) because a relatively large share of the benefits for these alternatives is associated
with travel time savings (while productivity benefits from LCV operations account for a large
share of the benefits for this alternative). This would mean that the relative difference in per-
formance of mixed-flow lanes and truck-only lanes without LCV operations might not change
much with a decrease in congestion levels (compared to the conditions defined in this analy-
sis), but the relative performance of the truck-only lane alternative with LCV operations com-
pared to the mixed-flow lane alternative is expected to improve. In other words, decrease in
corridor congestion levels would potentially bring the minimum diversion threshold for cost-
effectiveness of the truck-only lane alternative to lower than 30%.
· As noted in the introduction to this chapter, the results in Figure 4.1 very likely underestimate
the benefits of truck-only lanes because they do not fully account for the safety benefits of
truck-only lanes as compared with additional mixed-flow lanes. This shortcoming is unlikely
to significantly alter the conclusions since safety benefits are a relatively small contributor to
overall benefits.
· The analysis does not take into account potential market diversion from congested rail corri-
dors to the LCV lanes, which could add further benefits without any increase in costs, partic-
ularly in cases where LCV lanes provide significant improvements in reliability, speed, and
productivity, leading to diversion from rail to LCVs. Market diversion from rail to LCV cor-
ridors was not taken into consideration because this type of analysis is typically corridor spe-
cific, and would require extensive market analysis to assess the types of commodities along the
corridor being studied, commodity O-D patterns, and shipper surveys to assess the propen-
sity for cargo diversion from rail to LCVs, which was beyond the scope of this study. How-
ever, it would be critical to account for modal diversion in the feasibility analysis of CMV-only
lanes (with LCV operations) along long-haul corridors as part of future research (it is antici-
pated that the consideration of truck-rail diversion typically would be based on a case-by-case
basis, depending on the conditions along specific long-haul corridors being studied for the
feasibility of implementing CMV-only lanes).
4.7.2 Urban Corridor
As in the case of the long-haul corridor scenario, the B-C analysis to evaluate the cost-
effectiveness of truck-only lanes compared to adding mixed-flow capacity on urban corridors
was based on a sensitivity analysis approach that involved analyzing the variations in B-C ratios
for the truck-only lane alternative as a function of diversion rate, and comparing these results with
the benefit-cost for the additional mixed-flow lane alternative to identify the range of diversion
rates for which truck-only lanes are observed to be cost-effective when compared to adding
mixed-flow capacity. The following sections present the costs, monetized benefits, and compar-
isons of benefit-cost between the urban corridor alternatives for various diversion rate scenarios.
Costs
This section quantifies the various cost components associated with implementing the build
alternatives for the purpose of conducting a comparative B-C analysis, using the unit cost esti-
mates presented in an earlier section, and the configurational characteristics of the urban generic
corridor. As with the long-haul corridors scenario, due to uncertainties in costs associated with
implementing truck-only lanes, which could be impacted by corridor (such as number of inter-
changes) as well as demand characteristics (which would potentially impact O&M costs), the
B-C analysis uses a range of costs as part of the sensitivity analysis. The range of costs was devel-
oped by first estimating a baseline total cost for each alternative, and varying the costs across the
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74 Separation of Vehicles--CMV-Only Lanes
Table 4.7. Baseline cost components for urban corridor alternatives,
in billions of dollars (indexed to 2008).
Mixed-Flow Truck-Only Lanes
Costs Lanes (without LCV Operations)
ROW Acquisition 0.1 0.1
Construction (Lanes) 0.2 0.4
Construction (Interchanges) 0.4 0.4
O&M 0.1 0.1
Total 0.8 1.0
baseline (lower and upper limit costs with the baseline as the mean), using a variance of ±20%
relative to the baseline.
Table 4.7 presents the baseline cost components for the urban corridor alternatives. A detailed
discussion of the approach to calculating costs and their relationship to the NPV analysis is pre-
sented in Appendix C.
Similar to the B-C analysis for long-haul corridors, to account for the uncertainty in costs in
the sensitivity analysis, the total costs for each alternative are varied to arrive at a representative
range of cost estimates for the B-C analysis. Table 4.8 presents these cost variations for the urban
corridor alternatives.
Monetized Benefits
As in the long-haul corridor scenario, a range of diversion rates is considered in the B-C analy-
sis to assess the impact of diversion rates on the performance benefits of truck-only lanes and
identify the range of diversion rates for which truck-only lanes are observed to be cost-effective
when compared to adding mixed-flow capacity along urban corridors. The results for the mon-
etized benefits under each performance measure for each alternative under different diversion
rate assumptions are presented in Table 4.9. Note that the results for the additional mixed-flow
lane alternative do not change under different diversion rate scenarios because they are only
applicable to the truck-only lane alternative.
Benefit-Cost Results
Figure 4.2 shows the comparison of B-C results for each alternative as a function of diversion rates.
Conclusions
Following are some of the caveats associated with the current analysis, which are important
to note before discussing the key conclusions from the results in Figure 4.2:
· The B-C ratios from the NPV analysis for the mixed-flow and truck-only lane alternatives are
observed to be significantly high, and should be viewed with caution. Since the B-C results are
Table 4.8. Range of costs considered for the B-C analysis, in billions of dollars
(indexed to 2008).
Lower Limit for Cost Baseline Upper Limit for Cost
Alternative (20% Below Baseline) Cost (20% Above Baseline)
Mixed-Flow Lanes 0.6 0.8 1.0
Truck-Only Lanes 0.8 1.0 1.2
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Benefit-Cost Analysis 75
Table 4.9. Monetized benefits of alternatives for different diversion rate
assumptions, in billions of dollars.
Additional Mixed-Flow Lanes Truck-Only Lanes
Diversion Travel Travel
Rate (%) Time Reliability Safety Total Time Reliability Safety Total
10 5.6 1.5 0.4 7.4 1.5 0.4 0.1 2.1
20 5.6 1.5 0.4 7.4 2.8 0.9 0.3 3.9
30 5.6 1.5 0.4 7.4 3.8 1.3 0.4 5.5
40 5.6 1.5 0.4 7.4 4.6 1.7 0.5 6.8
50 5.6 1.5 0.4 7.4 5.2 1.9 0.5 7.6
60 5.6 1.5 0.4 7.4 5.5 2.0 0.6 8.1
70 5.6 1.5 0.4 7.4 5.5 2.0 0.6 8.1
80 5.6 1.5 0.4 7.4 5.1 2.1 0.6 7.7
90 5.6 1.5 0.4 7.4 4.0 2.0 0.6 6.6
100 5.6 1.5 0.4 7.4 2.1 1.9 0.6 4.6
a function of a range of factors, including the demand and configurational characteristics of the
representative baseline corridor (as mentioned earlier, the defined conditions along the base-
line generic corridor may not be fully representative of conditions along an actual corridor,
which may have an impact on B-C results), the time horizon for the NPV analysis, the benefits
monetization factors (e.g., value of time estimates) used in the analysis, and uncertainties in the
costs, the B-C results in Figure 4.2 are used only to assess the relative B-C performance between
the mixed-flow and truck-only lane alternatives, and are not for assessing the B-C performance
of each of the build alternatives individually against the no-build alternative.
· The estimation of the performance benefits of alternatives does not consider differences in
time-of-day distributions between auto and truck traffic volumes, which could potentially
impact the benefits of truck-only lanes, and consequently, the relative B-C performance of
truck-only lanes when compared to adding mixed-flow capacity. For the interpretation of the
14.0
12.0
10.0
8.0
B/C
6.0
4.0
2.0
-
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Diversion Rate
Mixed Flow Lower B/C Limit Mixed Flow Baseline B/C
Mixed Flow Upper B/C Limit Truck only Lane Lower B/C Limit
Truck only Lane Baseline B/C Truck Only Lane Upper B/C Limit
Figure 4.2. B-C results for alternatives as a function of diversion rate.
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76 Separation of Vehicles--CMV-Only Lanes
results in Figure 4.2, it is assumed that time-of-day differences between auto and truck vol-
umes for the representative baseline corridor are not significant, and therefore, would not
impact the performance of truck-only lanes.
· Due to a lack of robust analytical tools to assess the true safety benefits of truck-auto separa-
tion (which also impacts the accuracy of the estimation of reliability benefits of truck-only
lanes), the results in Figure 4.2 could be amiss in providing insights into the relative B-C per-
formance of truck-only lanes when compared to adding mixed-flow capacity, particularly
along corridors where safety and reliability issues caused by truck-auto interactions are a
major concern.
Given the above caveats, however, the results in Figure 4.2 are useful in gaining insights into
the relative B-C performance of truck-only lanes when compared to additional mixed-flow lanes,
which are discussed as follows:
· Clearly, as observed under the long-haul corridor scenario, truck diversion rates have a direct
impact on the B-C performance of truck-only lanes. Truck diversion rates of 60% to 70% pro-
vide the highest B-C ratios for the truck-only lane alternative. Very high diversion rates
(greater than 80%) impact overall performance under this alternative as the truck-only lanes
begin to experience congestion and the system does not have optimal capacity utilization
(both on the general purpose and truck-only lanes). Since trucks have a higher value of time
when compared to autos (more than 2.5 times auto value of time in the current analysis),
mobility on truck-only lanes is important for the truck-only lane alternative to achieve high
levels of performance benefits in monetary terms. The importance of this result is significant
in analyzing policy issues associated with the use of truck-only lanes (e.g., in this case, manda-
tory use of truck-only lanes might not be a feasible policy option because it would not ensure
optimal system performance). The B-C performance of the truck-only lane alternative is
observed to be low under low diversion rates because there is under-utilization of truck-only
lane capacity, and low levels of diversion from the general purpose lanes result in low level of
congestion relief from these lanes. These relationships are important in understanding the
impacts of tolls on truck-only lanes, since higher tolls can impact diversion rates, thus affect-
ing the benefits of truck-only lanes as well as the revenue potential of tolls.
· Comparing the B-C performance of mixed-flow and truck-only lane alternatives, the mixed-
flow lane alternative is observed to generally have a better B-C performance when compared
to the truck-only lane alternative under the defined conditions of the representative baseline
corridor (although there is a range in the graph where the truck-only lane alternative could
have a better performance given the uncertainties in the costs and the variations in the diver-
sion rates). This can be explained to a certain extent from the results in Table 4.9, which indi-
cate that a large share of the benefits for both the alternatives is driven by congestion
reduction (travel time savings). These results suggest that for truck-only lanes to have a
higher B-C performance when compared to mixed-flow lanes, in addition to travel time sav-
ings, they have to provide significantly higher safety and reliability benefits (compared to
mixed-flow lanes), which is not being achieved in this case. The implications of this obser-
vation include the following:
As mentioned earlier, the safety and reliability benefits of truck-only lanes (associated with
truck-auto separation) were estimated based on a post-processing approach, which
involved application of accident reduction factors, without the use of robust analytical tools
such as simulation. Consequently, the post-processing approach could potentially be
underestimating the true safety and reliability benefits of truck-auto separation. Given the
constraints in the current project, it would, therefore, be important to supplement these
results with more detailed analyses of the safety and reliability performance of truck-only
lanes to understand the magnitude of these benefits in relation to the mobility benefits of
truck-only lanes.
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Benefit-Cost Analysis 77
The results do, however, provide insights into the types of corridor applications under
which truck-only lanes could be expected to have a better B-C performance (relative to
mixed-flow lanes) compared to the observations in Figure 4.2. For example, the results sug-
gest that truck-only lanes could be more viable compared to mixed-flow lanes on corridors
for which, in addition to congestion mitigation, there are specific performance improve-
ment needs that could be better met by truck-auto separation than by adding mixed-flow
capacity, which may include the following:
Congested urban corridors on which, because of terrain such as grades and other system
configurational issues, there may be safety problems due to truck-auto operational con-
flicts. Implementation of truck-only lanes along these corridors would provide signifi-
cant levels of safety and reliability benefits in addition to travel time savings from
diversion of trucks from the general purpose lanes.
Urban corridors serving as key access routes to major freight facilities (such as seaports)
where high truck and auto volumes, in addition to causing congestion, may be leading
to reliability problems for international goods movement supply chains relying on the
corridor for truck shipments. Along these corridors, the implementation of truck-only
lanes would not only relieve congestion on the general purpose lanes by diverting trucks,
but also provide dedicated lanes for port truck traffic, resulting in improved truck freight
mobility and reliability.
