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84 Separation of Vehicles--CMV-Only Lanes because safety benefits are observed to be a relatively small contributor to overall benefits. Also, the analysis does not take into account potential market diversion from congested rail corridors to the LCV lanes, which could add further benefits without any increase in costs; however, the impact of this to the overall B-C results is not expected to be significant. 5.2 Truck-Only Lanes in Urban Corridors Urban corridor applications of truck-only lanes have been identified in locations with some of the following characteristics: Congested corridors with high truck volumes and significant contribution of truck traffic to congestion (e.g., I-710 and SR 60 in Southern California); Major through-truck routes that go through metropolitan areas and have high truck volumes and congestion (e.g., the Mid-City Freightway in Chicago and I-5 in Seattle); and Congested corridors providing access to major ports or intermodal facilities (e.g., I-710 in Southern California, Miami Tunnel, and Savannah, Georgia). The primary objectives governing the implementation of truck-only lanes in urban areas are the following: Reducing congestion but because many of the urban studies compare truck-only lane alter- natives to alternatives that do not provide equivalent capacity expansion with general purpose lanes, it is difficult to draw conclusions about how effective and under what circumstances truck-only lanes would be cost beneficial. Even assuming equal congestion relief benefits for truck-only lanes as compared to general purpose lanes, the choice of truck-only lanes may be driven by the belief that trucks would pay higher tolls to avoid congestion and that this pro- vides a more effective approach to financing capacity needs. Truck driver willingness to pay tolls may be overestimated, however, in many of the studies conducted to date. Mitigating impacts of truck traffic in high-truck-volume corridors by diverting trucks to cer- tain corridors, improving flows (thus reducing emissions), and getting trucks off arterials. Separating trucks from autos, thus improving safety and providing reliability benefits (due to reduction in incident-related delay). Providing improved travel times and reliability for trucks serving ports and intermodal sites to maintain the economic viability and competitiveness of these facilities. Complementing innovative freight-oriented land use strategies (e.g., inland ports or freight vil- lages). Truck-only lanes can be constructed to link facilities like inland ports to primary port facilities, making operations more economical. No research was identified where efforts were made to estimate the degree to which truck-only lanes would be beneficial in encouraging these types of freight-oriented land use strategies or making them more cost effective. Facilitating the implementation of truck automation (truck platooning) and/or truck electri- fication strategies, electronic toll collection (ETC) strategies using automatic vehicle identifi- cation (AVI) technologies, and improved weight and safety enforcement of trucks. 5.2.1 Feasibility Criteria The feasibility of implementing truck-only lanes on urban corridors is a direct function of corridor demand and system characteristics, including truck and auto traffic volumes, share of truck traffic of total traffic, time-of-day variations in truck and auto traffic volumes and con- tribution of truck traffic to peak-period congestion, truck routing and O-D patterns, length of corridor, and number of lanes. An understanding of the various truck-only lane feasibility cri- teria would be useful in corridor planning projects, particularly in the preliminary alternatives development processes, to determine the viability of including truck-only lanes for detailed alternatives analyses.

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Conclusions and Recommendations 85 The Douglas handbook serves as a compendium on the key quantitative factors to be con- sidered in assessing the feasibility of truck-only lanes, the recommendations of which are sum- marized as follow: Bidirectional daily total traffic volume on the corridor should be at least 15,000 per lane. Bidirectional daily total truck52 volume on the corridor should be at least 20,000 trucks per day. Bidirectional daily total truck volume should exceed 20,000 trucks for a minimum distance of 10 mi along the corridor, or the corridor should provide access to major freight generators at the termini. The corridor on which truck-only lanes are to be implemented should have at least two general purpose lanes in each direction. Also, truck-only lanes should have at least two lanes in each direction. There has been limited research on the impacts of variations in time-of-day distributions of trucks and autos on the feasibility of truck-only lanes, which is a key data gap that needs to be addressed in future research. The next section provides further discussion of the impacts of time- of-day differences on the ability of truck-only lanes to provide peak-period congestion reduction benefits. 5.2.2 Mobility In the evaluation of the mobility benefits of truck-only lanes on urban corridors, it is critical to assess the relative performance and cost effectiveness of truck-only lanes compared to adding mixed-flow capacity. As part of the performance evaluation task of the project, the differences in capacity assumptions between the truck-only lane and mixed-flow lane alternatives, and the omis- sion of the mixed-flow lane alternative in the performance evaluation in some of the reviewed studies, has resulted in the findings being inconclusive or inadequate in assessing the relative per- formance benefits of truck-only lanes against mixed-flow lanes with similar capacity. The B-C analysis approach undertaken in this study has attempted to address this gap, the key conclusions from which are summarized in a later section of this chapter. With respect to the application of truck lanes to reduce congestion on urban corridors, most of the analysis has been done with traditional travel demand models. All other features of truck-only lanes versus general purpose lanes being equal, the only way that truck-only lanes would compete favorably with general purpose lanes for congestion relief would be if trucks have a significant impact on congestion during the peak periods (periods with high levels of congestion), and the truck-only lanes are highly utilized during peak periods (by affecting significant truck diversion from the general purpose lanes). This suggests that there are threshold volumes of trucks below which truck-only lanes are not likely to achieve the benefits that could be obtained from additional general purpose lanes. The traffic threshold volumes for assessing the applicability of truck-only lanes typically pertain to total daily truck and total traffic volumes, as suggested by the Douglas report (which are discussed in the previous section). It should also be noted that much of the analysis of truck-only lanes that has been done to date has been done based on daily models, models which do not consider the differences in time-of-day distributions of trucks and autos, or models in which the time-of-day distribution of trucks is not based on accurate data. It is absolutely critical to not only understand daily demand but to under- stand peak-period and peak-hour truck and auto travel demand. Trucks tend to favor mid-day operation in urban areas and generally avoid peak periods to the maximum extent possible. This means that demand for truck-only lanes would be highest during the least congested periods of the 52 Heavy-duty trucks with three or more axles are included in this category.

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86 Separation of Vehicles--CMV-Only Lanes day. Analysis in the I-710 and SR 60 studies show this in general terms. This could have major implications for the success of tolling concepts based on the accurate estimation of potential toll revenues. To summarize, it is likely that studies that do not take time-of-day distribution of truck activity into account have overestimated the benefits of truck-only lanes. On the other side of the balance sheet, travel demand models may underestimate the average travel time savings benefits to all motorists of having trucks and autos separated based on the way PCEs are calculated. There is evidence from many studies that PCE values vary with congestion conditions and the amount of trucks in the flow when trucks and autos mix. This is related to the acceleration/deceleration characteristics of trucks as compared to autos, and the effects of merg- ing and weaving. It has been further hypothesized that in urban driving conditions trucks may travel at lower average speeds than autos even within the same traffic conditions and thus PCE val- ues need to be recalibrated. The most sophisticated travel demand model in terms of capability to examine this effect is the SCAG HDT model, which does employ variable PCE factors for trucks. However, additional research into how to calibrate variable PCE factors in different flow condi- tions as well as for situations in which trucks represent the entire flow, as in truck-only lanes would be helpful in improving the accuracy of travel demand models in measuring the travel time savings benefits of truck-only lanes. Based on future improvements in the ability to assess the true mobil- ity benefits of implementing truck-only lanes for autos on general purpose lanes, it could be that the mobility benefits for the general public (autos) potentially turn out to be a stronger selling point to policy makers for the implementation of truck-only lanes compared to the benefits associated with improved operational efficiencies for trucking companies. 5.2.3 Safety and Reliability The results from the performance evaluation task consistently indicate that truck-only lanes have higher safety benefits compared to mixed-flow lanes. However, the results are inconclusive in understanding the "true" incremental safety benefits of truck lanes because of the differences in capacities between the truck-only and mixed-flow lane alternatives considered in the studies, as well as some key limitations in the approaches used to analyze the safety benefits of truck-only lanes, which are discussed in this section. It is observed from the review of studies conducted as part of the performance evaluation process that the general approach to estimating the safety benefits of truck-only lanes on urban corridors has been to quantify the reduction in accidents from congestion relief (on the general purpose lanes due to diversion of trucks to truck-only lanes, and to some extent on the truck-only lanes due to improved mobility), without typically accounting for the safety improvements from truck-auto separation. The analysis that was conducted in the performance evaluation task using the data from various studies and presented in Chapter 3 attempts to introduce some assessment of the safety benefits of separating trucks and autos, based on application of post-processing factors to account for safety improvements of truck-auto separation as recommended by the Douglas handbook. The Douglas handbook recommends a reduction factor of 15% for accidents to account for the safety benefits of truck-auto separation. This factor was derived based on an evaluation of historic crash data on the New Jersey Turnpike, which indicated that total crash rates along the dual-dual roadway sections (sections with auto-only lanes and mixed-flow lanes) of the turnpike reduced by 18% during the first 5 years of dual-dual roadway operations (the dual-dual roadway sections were first implemented in 1966). More recently, in the 1994 to 2003 time period, the dual-dual roadway sections were observed to have accident rates at least 28% lower than the mixed-flow sections of the turnpike. The Douglas handbook concluded that the actual safety benefits of the dual-dual sec- tions (accounting just for the benefits realized from separating autos from the mixed-flow lanes, and not considering the safety benefits from increased capacity on the dual-dual roadway sections)

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Conclusions and Recommendations 87 are expected to be closer to the 18% reduction factor, since the impacts of increased capacity on safety are not expected to be significant during the initial phases of implementation. Given the rec- ommendations from the Douglas handbook based on historic data from the New Jersey Turnpike, there still remain, as mentioned under the long-haul corridors section, a number of opportunities to improve the state of knowledge pertaining to the actual safety benefits of truck-only lanes result- ing from separation of trucks and autos. One of the simplest but yet persuasive methodologies for conducting a robust analysis of the safety benefits of truck-only lanes is the application of different crash rates per million VMT for truck-involved and auto-only accidents, which are applied to estimates of auto and truck VMT in truck-only lane configurations to assess the degree to which crashes are reduced. However, there appears to be a lack of available data on the variation in accident rates (by type of accident) as a function of truck shares (truck percent) of total traffic. This is an area of research that should be undertaken in the future to improve data inputs and analytical capabilities to accurately estimate the safety benefits of truck-auto separation. A proposed framework to estimate the dependence of accident rates on truck shares and other corridor characteristics (such as grades and number of lanes) has been presented under the long-haul corridors section. This would be applicable to urban corridors as well. In future studies, there should be ways to develop simulation models of the operations of truck- auto separations to see the degree to which "near-crash" situations are simulated. Assuming some probability that these would develop into actual crashes, it should be possible to simulate numbers of crashes that could be avoided with truck-auto separations. The application of simulation mod- els in analyzing the safety benefits of truck-auto separation has also been demonstrated from research conducted at the University of Tennessee, Knoxville.53 Under this research, the approach used to analyze safety benefits involved simulating alternatives (truck-only lanes and no-build) in a VISSIM microsimulation environment, using number of lane changes per hour (lane change rate) as the performance metric for safety analysis, under the assumption that higher lane change rates would result in a higher propensity for accidents and lower safety performance. This research estimated a 47.3% reduction in lane change rate due to truck-auto separation. One other approach that could be used to develop more data on the safety (and travel time) ben- efits of truck-auto separation would be to set up experimental truck-only lanes and collect data on different configurations. A basis for conducting these experiments can be found in a recent study conducted by NCTCOG, the Dallas-Ft. Worth Metropolitan Planning Organization (MPO). In this study, NCTCOG was trying to determine the impacts of restricting trucks to the two right- hand lanes. NCTCOG set up short-term experiments that implemented the lane restrictions and then used video and on-site operations to document changes in relative travel speeds by lane, crash rates by lane, frequency of near-miss accidents, and amount of queuing backups on to the freeway or at on ramps. Staff at NCTCOG think it would be difficult to conduct comparable experiments because of the potential for degraded traffic operations without being able to upgrade merge and weave sections and design new interchanges. It would appear that the best opportunities to con- duct such experiments would be those where the truck-only lanes could be fully separated with sep- arate interchanges to and from the truck-only lanes. Potential applications could include the conversion of HOV lanes or busways to truck-only lanes for a short period of time for the purpose of this type of analysis. There were no studies identified in this project that tried to take the estimates of crash reduc- tion benefits of truck-auto separation further and estimate reductions in incident-related delay 53 A. A. Adelakun, Simulating Truck Lane Management Approaches to Improve Efficiency and Safety of Highways in Knoxville, Tennessee, Master of Science thesis, University of Tennessee, Knoxville, December 2008.

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88 Separation of Vehicles--CMV-Only Lanes and associated reliability improvements. The general estimates of reliability benefits that have been incorporated in a few of the studies suffer because generally they base reliability benefits in terms of savings in incident-related delay on correlations between variables such as VMT, number of lanes, and V/C ratios (i.e., to factors related to general congestion and not to truck- auto separation) to establish the amount of nonrecurrent (incident related) delay. The post- processing effort conducted in this study accounted for this deficiency by applying the accident reduction factor recommended by the Douglas handbook to account for the incremental sav- ings in incident-related delay due to accident reduction from truck-auto separation. It is noted, however, that there is a need for improved analytical methods to better understand the true reli- ability benefits of truck-only lanes. A more sophisticated approach would be to use simulation models to estimate actual travel times and travel time variability. In this approach, the simula- tions would examine queue build-up and clearing effects with mixed and nonmixed flows under congested conditions and when accidents occur. Truck-involved crashes generally are more severe and take longer to clear. Thus, queues tend to build up for long periods of time when a heavy-duty truck is involved. The primary difficulty in applying simulation methods is the cali- bration of simulation models for truck-only conditions. As previously described, there may be some experimental approaches where separated lanes (such as HOV lanes or busways) are tem- porarily dedicated to truck-only conditions in order to examine changes in crash levels and incident-related delays, and to use these data to calibrate the simulation models to assess safety and reliability benefits of truck-only lanes. 5.2.4 Port and Intermodal Terminal Access In areas around ports and intermodal terminals, the research suggests there can be real benefits to communities--beyond the congestion, safety, and reliability benefits discussed previously--by directing and diverting truck traffic to preferred corridors and routes. Studies such as the Mid-City Freightway54 in Chicago, Miami Toll Truckway: Preliminary Feasibility Study,55 and I-710 Major Corridor Study56 show that new truck routes or truck-only lanes on existing corridors that are designed to serve industrial areas, port and intermodal terminals, and customers in dense urban settings can relieve pressure on mixed-flow freeways by providing alternative routes better aligned with existing and forecast truck flows. This has been demonstrated in most of these connector studies. These studies also show that if main connectors are very congested, truck traffic often spills out onto arterial streets. Truck-only lanes may be more effective in providing relief in these situa- tions than adding general purpose capacity because the truck lanes may be less congested and provide a very beneficial alternative for trucks. They can also be planned with alignments and entry/egress locations that more closely match the routing and O-D patterns of trucks accessing the port and intermodal terminals. Another benefit of planning truck lanes to serve ports and intermodal terminals is that they tend to exhibit node-to-node travel characteristics that are not otherwise characteristic of urban truck travel. Examples include connections between ports and off-dock intermodal terminals, logistics parks, and other concentrations of warehouse/distribution facilities. This allows for the design of a facility with more limited access and this can be very cost-effective. In more general urban truck corridors, limiting access can have significant impacts on usage levels. Studies such as those on SR 60 and I-710 illustrate this point clearly. 54 Chicago Department of Transportation, Mid-City Freightway: Evaluation of Alternative Alignments and Tolls, November 2006. 55 R. W. Poole, Jr., Policy Study 365, Miami Toll Truckway: Preliminary Feasibility Study, Reason Foundation, November 2007. 56 Los Angeles County Metro, I-710 Major Corridor Study: Final Report, March 2005.

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Conclusions and Recommendations 89 Several studies have examined the amount of time savings per trip for average trips between ports and inland warehouses. To the extent that these time savings add up over the course of a day to allow drayage operators to make extra trips and generate extra revenue, they may be able to pass some of these savings on to shippers. However, to date no studies have been able to demon- strate the degree to which these savings increase the competitiveness of ports. Leachman57 con- ducted an analysis of modal cost and congestion elasticities for SCAG by examining the impacts of fees on port and distribution channel choices. Leachman's model has been used to examine the effect of spending cargo fees on reducing congestion at the marine terminals as a tradeoff against the economic impact of the fee by itself. The congestion impacts that Leachman exam- ined to date are focused on queues at marine and intermodal terminals and capacity constraints on rail mainlines. His models have not yet incorporated the impacts of delay on access roadways as it affects port and distribution channel choices. It would be possible to build this capability into Leachman's models by conducting simulations of critical access corridors with and without truck lanes in order to establish mean travel times between nodes and standard deviations in these times. It is recommended that the scale of delays associated with roadway congestion be compared to the scale of other delays in the logistics system and the demand elasticities associated with delays to determine whether it would be cost-beneficial to develop this type of analytical capability. 5.2.5 Tolling Urban Truck Lanes The potential for tolled truckways in urban corridors is controversial and the analysis to date is inconclusive as to how cost-effective this approach may be. However, the I-710 Major Corridor Study conducted sensitivity analysis of various toll scenarios to assess the impacts of tolls on diver- sion potential and utilization of truck-only lanes, which provide some useful insights. The study provides relationships between changes in tolls and diversion to truck-only lanes that can be used to understand how tolls impact the performance of truck-only lanes based on truck and auto vol- ume characteristics on the general purpose lanes, as well as assess the revenue potential of various toll scenarios. Figure 5.1 depicts the results of the sensitivity analysis in terms of the impacts of tolls on utilization of truck-only lanes along the corridor. These results pertain to a truck-only-lane toll scenario with voluntary use of truck-only lanes. It would be important to note that the performance of tolled truck-only lanes would be different under mandatory usage of truck-only lanes (all trucks diverting from the general purpose to truck-only lanes), since the diversion rate in that case would not depend on the magnitude of the tolls. As expected, the highest diversion occurs under the no-toll scenario, in the range of 50% to 90% of total truck traffic along the corridor. With the application of tolls of $0.07 per mile, the estimated diversion drops to between 30% and 70%. With tolls of $0.15 per mile, the diversion further drops to between 10% and 30% along the corridor. In deciding on the application of tolls on truck lanes, it is not only important to analyze the rev- enue potential of tolls to recover the costs of developing truck lanes, but also to look at the impacts of tolls on congestion on the general purpose lanes and the effective utilization of truck lanes. Tolls resulting in low truck diversion from general purpose to truck lanes would not contribute to an effective investment strategy due to substantial underutilized capacity on the truck lanes, as well as marginal reduction in congestion on the general purpose lanes. The diversion potential of tolled truck lanes is also important because some share of the freed-up capacity could potentially be filled up by autos diverting to the general purpose lanes from arterials, as well as some trips outside the region that now use the corridor due to the increased capacity. 57 R. C. Leachman, et al., Port and Modal Elasticity Study, Southern California Association of Governments (SCAG), September 2005 (http://www.ieor.berkeley.edu/People/Faculty/leachman-pubs/PortModal.pdf).

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90 Separation of Vehicles--CMV-Only Lanes SR-60 Fwy I-5 Fwy Washington Blv AtlaPMic/Bandi Florence Blvd Firestone Blvd Imperial Hwy Location along I-710 I-105 Fwy Rosecrans Avn Alondra Blvd SR-91 Fwy Artesia Blvd Long Beach Blv Del PMo Blvd I-405 Fwy Wardlow Road 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent of I-710 Trucks on Truck Lanes Truck lane Usage 15c Truck lane Usage 7c Truck lane Usage No Toll Source: Adapted from Los Angeles County MTA, 710 Major Corridor Study--Final Report, March 2005. Figure 5.1. Impact of tolls on truck lane utilization. Some of the key factors that would impact the decisions related to the application of tolls on truck lanes include, but may not be limited to, the following: Revenue potential of tolls and what share of the costs of developing truck lanes can be recov- ered through tolls. The revenue potential of tolls is tied to the diversion potential of tolled truck lanes for a given toll scenario, which is in turn dependent on the congestion and reliability benefits of truck lanes and the value of time distribution of truck traffic along the corridor. Magnitude of truck and auto traffic volumes, congestion along the corridor, and contribution of truck traffic to corridor congestion. To benefit from truck-only lanes under a toll scenario, there needs to be significant congestion along the corridor and truck traffic needs to be a sig- nificant contributor to congestion. Truck traffic with high sensitivity to travel time and reliability benefits. This factor would be inherently dependent on the value of time and reliability distributions of truck traffic. Typically, urban corridors with significant port truck traffic volumes such as I-710 would have favorable conditions for application of tolls, because a large share of the port truck traffic would be willing to pay tolls to achieve improved travel times and reliability.

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Conclusions and Recommendations 91 Variable tolling. Variable tolling might be a potent approach to maximize the truck diversion, utilization, and revenue potential of truck lanes along corridors with varying congestion, and truck and auto volume characteristics by time of day. As noted, the benefits that truckers can realize from operating on tolled truck lanes are tied to the congestion conditions on the general purpose lanes. Based on the analysis conducted to date, it is understood that in cases where there are significant differences in time-of-day characteristics of trucks and autos (e.g., trucks predominantly operating in the mid-day period that is less con- gested), tolled truck-only lanes constructed next to existing general purpose lanes may not provide great enough benefits to truckers to affect diversion from the mixed-flow lanes to the truck lanes. Other studies have suggested that delays while on freeways (especially for short urban goods move- ment trips) may be relatively small as compared to delays at loading and unloading locations, sug- gesting that willingness to pay tolls may also be relatively low and potential revenues from tolled truck lanes in urban settings may not generate sufficient revenue to cover much of the cost of the lanes. Staff at SCAG have conducted novel analysis of how taking reliability into account may alter this conclusion.58 The way that truck owners and shippers deal with unreliability is poorly under- stood, and the affects of travel time reliability benefits of truck-only lanes on willingness to pay tolls is not adequately addressed in most truck-only toll lane studies. 5.2.6 LCV Operations in Urban Corridors The benefits of LCV operations in urban corridors are likely to be very limited except in certain limited applications. In urban corridors, trucks will only spend a fraction of their trip time on free- ways that might have truck-only lane options while a significant amount of time will be spent off the truck-only lane system accessing local destinations. Off system, trucks will not be able to oper- ate as LCVs. Siting staging areas and absorbing these costs could limit the cost-effectiveness of LCV operations in urban corridors. The one exception could be cases where truck-only lanes provide high-volume connections between two major freight nodes (e.g., between a port and an off-dock intermodal terminal). In these instances, the LCVs will have limited or no time off the LCV truck lanes and the productivity benefits can be applied to many repeated trips. The limited number of urban corridors that have examined LCVs is further evidence of the limitations of this approach. 5.2.7 Applications of Automation Technologies Automated guidance systems and Cooperative Vehicle Highway Automation Systems (CVHAS) appear to have significant potential benefits on truck-only lanes in urban corridors based on the analysis conducted by Shladover.59 These systems offer benefits in terms of reduced travel times, increased safety, reduced energy costs (and potential environmental benefits associated with smoother vehicle flows and efficient operations to reduce CO2 emissions), and increased through- put of the lanes. See Table 2.3 for a demonstration of this conclusion by way of comparison with other alternatives. The potential for increased throughput in urban areas where right-of-way is often constrained is a major benefit of automated guidance in truck-only lanes. The Shladover work suggests that market timing of advanced technologies to ensure high levels of market penetration is important in determining the cost-effectiveness of the option. In high-truck-volume urban corridors, 58Southern California Association of Governments, Goods Movement in Southern California: The Challenge, the Opportunity, and the Solution, September 2005. 59S. E. Shladover, Advanced Vehicle Technologies and Exclusive Truck Lanes: Research from California PATH Program, Transportation Research Board Annual Meeting, Washington, D.C., January 2006.

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92 Separation of Vehicles--CMV-Only Lanes especially those that serve major freight nodes, it may be easier to achieve the levels of demand needed to make automation cost-effective. There are also interesting emerging concepts for phas- ing new technologies in truck-only lanes and CVHAS technology could be incorporated into these plans. For example, current work on the I-710 corridor in Los Angeles is examining a phased "freight corridor" development that could begin as truck-only lanes on a conventional viaduct structure to be converted to some type of electrified truck option (with wayside power systems or battery power) over time. Incorporating the phased development of CVHAS technology into this kind of evolutionary approach may improve the chances of success with the CVHAS technology. 5.2.8 Benefit-Cost Evaluation of Truck-Only Lanes on Urban Corridors The primary objectives of the B-C analysis of truck-only lanes on urban corridors were to assess the relative B-C performance of truck-only lanes compared to adding mixed-flow capacity based on an analysis of the key factors that drive the relative performance of truck-only lanes compared to mixed-flow lanes and under what conditions might truck-only lanes be a better alternative com- pared to mixed-flow lanes along urban corridors. The key conclusions from the B-C analysis on urban corridors are summarized as follows: Truck diversion rates of 60% to 70% provide the highest B-C ratios for the truck-only lane alternative. Very high diversion rates (greater than 80%) may not necessarily improve the performance of the truck-only lane alternative because 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). The importance of this result is significant in analyzing policy issues associated with use of truck-only lanes (e.g., mandatory 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 diver- sion rates because there is under-utilization of truck-only lane capacity, and low levels of diversion from the general purpose lanes result in a low level of congestion relief from these lanes. This observation is important in understanding the impacts of tolls on truck-only lanes, since higher tolls would impact diversion rates, thus affecting 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 generally to have a better B-C performance compared to the truck-only lane alternative (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 varia- tions in the diversion rates) under the defined conditions of the representative baseline corri- dor. This can be explained by the fact that a large share of the benefits for both the alternatives is driven by congestion reduction (travel time savings). The B-C results suggest that for truck-only lanes to have a higher B-C performance compared to mixed-flow lanes, in addition to travel time savings, they have to provide significantly higher safety and reliability benefits (compared to mixed-flow lanes). Due to a lack of analytical tools, the post-processing approach used for the B-C could potentially be underestimating the true safety and reliability benefits of truck-auto separation. Given the con- straints 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 with the mobility benefits of truck-only lanes. Based on the B-C results, some key insights can be gained on 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. These include