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Background and Key Concepts 9 related to toll truckway standards and interoperability. For example, the study talks about how FHWA could potentially sponsor an Operators and Shippers Forum for the exchange of ideas related to toll truckway planning and development. The importance of involving shippers in the CMV-only lane planning process would be critical in the case of analysis of LCV operations, since shipper inputs can be useful in understanding potential markets (types of commodities) along a corridor, and their propensity towards LCVs. The trucking industry has provided extensive com- ment on issues such as tolling CMV-only lanes (and associated trucking industry equity implica- tions) and LCV operations on CMV-only lanes. These positions are summarized in Appendix A. The planning issues surrounding mandatory versus voluntary usage of tolled truck-only lanes are also worth noting. The importance of this issue is underscored by the fact that the performance of truck-only lanes is a direct function of truck diversion (from general purpose to truck-only lanes), and tolls can directly impact the level of truck diversion in the case of voluntary usage of truck-only lanes. Also, mandatory usage of truck-only lanes may be associated with opposition from stakeholders, such as the carrier and shipper industry, which would be important issues to consider as part of any planning/policy making processes related to tolling truck-only lanes. In the case of voluntary usage of tolled truck-only lanes, it would be important to assess the impact of various toll scenarios (variations in toll rates) on utilization of truck-only lanes. This information would, in turn, be useful in determining the revenue generation potential under var- ious toll scenarios, as well as the performance of the corridor under each scenario, to arrive at a scenario that maximizes both the toll revenue as well as corridor performance relative to other scenarios. Chapter 5 presents some key results from the work conducted in this regard as part of the I-710 Major Corridor Study. Mandatory usage of tolled truck-only lanes might be more applicable on truck-only lanes serving specific truck trip purposes, such as truck-only lanes serving major freight facilities like seaports. However, as stated earlier, the issue of industry opposition would be important to address as part of the planning process for these facilities. Another important aspect to analyze in the case of mandatory usage of tolled truck-only lanes is the mobility performance of the truck-only lanes, depending on the capacity of these lanes, and the magnitude of truck demand. For freight facilities generating high daily truck traffic, it would be important to ensure that the truck-only lanes have adequate capacity in order to ensure operational efficiencies on these lanes under mandatory usage. 2.2 Configuration and Design Issues This section presents a summary of the various types of CMV-only lane applications and the key configurational and design issues pertaining to them. This section is subdivided into the following subsections: Types of truck lanes, Methods of separation, CMV-only lane cross-sectional configurations, Right-of-way (ROW) requirements, Pavement design, Geometric and cross-sectional design issues, and Costs. Additional data and information on each of these subsections can be found in Appendix A. Structural design elements (such as those pertaining to bridges) associated with CMV-only lanes have not been covered in this study, because it was concluded that analysis to elucidate the key issues surrounding this aspect of CMV-only lane projects and their relative comparisons against other alternatives would require substantial resources that are beyond the scope of the current

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10 Separation of Vehicles--CMV-Only Lanes study. It is, however, noted that future research focusing specifically on structural design issues of CMV-only lanes, and how they compare with other alternatives in terms of costs, should be under- taken to supplement the results and inferences obtained from this study. Also, such research might be more relevant for application on a case-by-case basis (for example, in the case of a corridor study where elevated CMV-only lanes might be a viable alternative). 2.2.1 Types of Truck Lanes As noted in Chapter 1, there are a number of different types of CMV-only lane concepts that include interchange treatments, lane restrictions, and climbing lanes in addition to the mainline treatments that are the focus of this study. Mainline CMV-only treatments include exclusive truck lanes (ETLs), nonexclusive truck lanes, and dual-dual roadways. ETLs physically separate truck lanes from general purpose highway lanes either through the construction of barriers or through grade-separated structures. They also may have dedicated access/egress ramps. By completely sep- arating trucks and autos they minimize weaving and maximize safety benefits. Nonexclusive truck lanes are mainline lanes that are not barrier separated (often using rumble strips) and autos typ- ically weave through the lanes at access/egress ramps. The dual-dual roadway concept has been implemented along the New Jersey Turnpike, which consists of inner auto-only lanes and outer lanes that carry mixed-flow traffic and to which truck traffic is restricted. Other types of CMV-only treatments include the following: Truck interchange bypasses for the purpose of removing trucks from interchange merge areas where their presence could be potentially detrimental to interchange operations, as well as exac- erbating interchange safety issues. Truck climbing lanes for the purpose of separating slow-moving trucks from the highway main- lines to prevent their impacts on optimal traffic speeds on high grades. In addition to overall speed benefits these lanes offer safety benefits by reducing lane changes by faster-moving vehicles. Truck ramps have a similar operational function as interchange bypasses but with the focus on improving operations by allowing more efficient access and egress of trucks by reducing weav- ing conflicts. 2.2.2 Methods of Separation Fully separated lanes can involve at-grade lanes separated with a median strip, elevated sections, or tunnels. The latter separations have safety and operational benefits and may reduce right-of-way impacts but at a greater expense than the first option cited. Structural issues associated with these methods of separation that are unique to truck traffic are discussed later and in more detail in Appendix A. Jersey barriers, as used in the New Jersey Turnpike, are often provided in the case of exclusive CMV-only lanes (ECLs, i.e., CMV-only lanes that are physically separated from general purpose lanes) and dual-dual roadways to ensure complete separation of truck and auto flows. The general configuration of Jersey barriers in terms of the cross-sectional design features is governed by the need to develop a configuration that minimizes the possibility of collisions between opposing traf- fic movements, as well as minimizing the impacts on vehicles hitting the barrier. A detailed discus- sion of the configuration features of Jersey barriers is provided in McDevitt.6 The compendium of CMV-only lane information provided in Appendix A presents a summary of this information, including standards for height and cross-sectional dimensions in different applications. Rumble strips are a common feature on highways as a safety measure to mark separation in nonexclusive truck lanes. There are many factors that can favor the application of non-ECLs in lieu 6C. F. McDevitt, "Basics of Concrete Barriers," Public Roads, March 2000.

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Background and Key Concepts 11 of exclusive facilities for trucks, such as right-of-way (ROW) availability, costs, interchange and ramp requirements, and amount of truck traffic demand. Since the functional characteristics of rumble strips for non-ECLs would be the same as those applied for shoulders in mixed-flow facil- ities, the configuration of rumble strips for truck-auto lane separation applications is expected to follow the same standards developed by FHWA for mixed-flow facilities. 2.2.3 CMV-Only Lane Cross-Sectional Configurations Depending on ROW availability and the level of truck traffic, ECLs may include passing lanes to allow for truck passing maneuvers and access for safety vehicles. In long-haul corridors, these lanes can be short length sections placed at appropriate intervals in much the same way that railroad sidings are used. Passing lanes may not be required if shoulder widths are adequate to make them viable as breakdown lanes. In all situations, cross-sections must take into account general purpose lane requirements (lane- widths may be able to be reduced if trucks are restricted), barrier widths, and inner/outer shoul- ders (widths are related to separation and access functions). A study conducted by Middleton, et al.7 from the Texas Transportation Institute (TTI) on strategies for separating trucks from passenger vehicles presents various types of CMV-only lane facility configurations under different ROW scenarios. Key observations about configuration standards are summarized in Appendix A and include options for standards with respect to CMV- only and general purpose lane widths, Jersey barrier widths, shoulder widths, and median widths under different design conditions. This, and other referenced studies, provides cross-sectional views for various configurations. Middleton's study also provides guidance on cross-sectional design considerations related to truck passing, accommodation of disabled trucks, impacts of con- figuration elements on capital costs, accounting for future expansion possibilities, and account- ing for the efficiency and ease of exit/entrance maneuvers for trucks. Several other studies are summarized in Appendix A, including the I-710 Major Corridor Study (Los Angeles Metro), I-75 truck lanes study (Florida and Georgia DOT), and Reason Foundation studies of LCV proposals. All of these studies present alternative cross-sectional design concepts with their rationale for specific design features that may be appropriate in particular circumstances. Based on the literature review, the New Jersey Turnpike was identified as the only real-world application of the dual-dual roadway concept. The auto-only and mixed-flow lanes are physically separated from each other, and each is provided with its own access ramps to/from interchanges. Typical cross-sections are presented in Appendix A. Douglas8 provides a good discussion of truck ramp configuration issues that address concerns such as location, spacing, length, and geometry. 2.2.4 ROW Requirements Cross-sectional configuration of CMV-only lanes determines ROW requirements or vice versa. Therefore, the reader is referred to the discussion of cross-sectional configuration in Appendix A for information about ROW requirements. It should be noted that elevated CMV-only lane con- figurations are increasingly being proposed with innovative elevated structural design concepts such as box girders with slender columns, to minimize their ROW requirements. 7D. Middleton, S. Venglar, C. Quiroga, D. Lord, and D. Jasek, Strategies for Separating Trucks from Passenger Vehicles: Final Report, September 2006. 8J. G. Douglas, Handbook for Planning Truck Facilities on Urban Highways, August 2004.

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12 Separation of Vehicles--CMV-Only Lanes 2.2.5 Pavement Design CMV-only facilities will typically experience a higher degree of pavement wear-and-tear com- pared to mixed-flow facilities, due to the constant heavy truck loads, presumably at higher oper- ational speeds. A study conducted by Button et al.9 from TTI was identified as a major source providing a discussion of pavement design issues addressing truck traffic loads. The following information draws heavily from this study. Large stone asphalt mixtures (LSAMs) are increasingly finding applications in the design of heavy-duty flexible pavements. Research conducted by Mahboub and Williams10 points out that properly designed LSAMs can be potentially attractive candidates for construction in heavy-truck traffic routes owing to their high resistance to deformation. Researchers are of the opinion that one of the key factors in achieving cost-effective pavement designs for heavy truck lanes is the use of premium base materials. Ongoing projects being con- ducted by TTI for TxDOT involve field testing of experimental base materials that are expected to provide useful information for the evaluation of existing material specifications, particularly for heavy truck traffic conditions. A key issue that needs to be addressed in conjunction with the devel- opment of new material specifications for CMV-only lanes is the application of new construction methods. It is expected that the implementation of new material specifications will likely require changes in existing pavement construction practices such as placing and compacting of new pave- ment materials. There also has been an increasing focus on the potential applications of smart materials11 for heavy truck corridors, because their implementation is expected to have significant benefits asso- ciated with reduced costs of pavement maintenance and improvements in traffic safety. An exam- ple of a smart material would be a self-healing polymeric substance used in pavements that would automatically heal pavement cracks. Finally, post-tensioned continuously reinforced concrete pavement designs have been proposed for consideration for the CMV-only lanes for the Trans Texas Corridor (TTC) and some of the cited advantages would appear to have general applicability to CMV-only lanes. 2.2.6 Geometric and Cross-Sectional Design Issues Although highway mainline design standards typically account for the physical and operating characteristics of trucks in the design processes for geometrics (horizontal and vertical alignments) and cross-sectional features (lane widths, shoulder widths, etc.), it is expected that these design standards would not always be directly transferable to CMV-only lanes, because of factors such as differences in truck operating characteristics on CMV-only lanes compared to general purpose lanes (for example, CMV-only lanes would typically allow for higher truck operating speeds than would general purpose lanes). Also, CMV-only lanes supporting long-haul LCV operations would require the application of a separate set of design guidelines that specifically address the physical and operating characteristics of LCVs, which are quite different from those of regular combina- tion trucks. Appendix A summarizes the major geometric and cross-sectional design parameters that would be important to consider in the design of CMV-only lanes, including sight distance, horizontal and vertical alignment, and cross-sectional elements. 9J. W. Button, E. G. Fernando, and D. R. Middleton, Synthesis of Pavement Issues Related to High-Speed Corri- dors, Texas Transportation Institute, Research Report 0-4756-1, September 2004. 10K. Mahboub and E. G. Williams, "Construction of Large-Stone Asphalt Mixes (LSAMs) in Kentucky," Transportation Research Record 1282, Transportation Research Board, Washington, D.C., pp. 4144, 1990. 11Smart materials, as defined by Wikipedia (www.wikipedia.org), are materials whose properties can be signifi- cantly changed in a controlled fashion under external stimuli, such as temperature, moisture, stress, etc.