Practical Highway Design Solutions (2013)

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9 As noted in the previous chapter, several states referred to other terms as support for responding “yes” to implement- ing a practical-design-like procedure, if not a formal policy; these terms included design exceptions, CSS, 3R projects, VE, and flexible design. Although likely familiar to most readers, these terms are concisely described in this chapter because they will be referred to in the discussions of the six state profiles in the next chapter. Also, they are discussed in the context of the project development process and current design standards, guidelines and approaches. A more in- depth discussion of these and other design principles can be found in NCHRP Synthesis 422: Trade-Off Considerations in Highway Geometric Design (1). Project DeveloPment Process The AASHTO document, A Guide for Achieving Flexibil- ity in Highway Design (2), describes the four stages of the project development process, as illustrated in Figure 1 and summarized here: • Concept Definition—In this initial stage, the purpose and need for a project or improvement is identified. FHWA describes the purpose and need statement as the foundation of the decision-making process, influenc- ing the rest of the project development process, includ- ing the range of alternatives studied and, ultimately, the alternative selected (3). As shown in Figure 1, proj- ects can be identified from needs studies (e.g., pave- ment condition congestion and safety history), outside requests, or long-range transportation plans. In the AASHTO guide, it is noted that a key to context-sensitive planning and design is developing a clear understand- ing of the need for the project during this stage. This principle applies equally to Practical Design, because one of its tenets is developing the project to resolve the identified need. • Planning and Alternatives Development—In this stage, alternatives are proposed and studied, envi- ronmental and community impacts are assessed, and decisions are reached about the key physical, environ- mental, and operational aspects of the proposed proj- ect. Once the purpose and need for a project have been determined, high-level design criteria are selected. The basis for the project design criteria will gener- ally be the transportation agency’s design guidelines. Key high-level design decisions would include such factors as: – Design year – LOS – Type of facility—freeway, expressway, divided versus undivided, etc. The culmination of this stage is the selection of the pre- ferred plan or solution. The AASHTO guide emphasizes that the greatest opportunities and challenges for a flexible trans- portation solution occur during this stage—the same statement could apply to Practical Design. • Preliminary Design—In this stage the geometric ele- ments of the highway or street are developed in sufficient detail to establish their impacts and full right-of-way and construction requirements. Key design elements include establishing the design speed. • Final Design—In this stage the complete plans, speci- fications, and construction bid documents are prepared; all design elements have been established and usu- ally only minor revisions occur perhaps to save costs, improve constructability, or reflect refinements based on actual right-of-way acquisition negotiations. Design Policy, stanDarDs, anD guiDelines Each state has its own road design manual that provides stan- dards, guidance, and procedures to follow throughout the project development process. State DOTs generally follow the design guidelines provided by AASHTO, modified to meet their particular situation, condition, and policy. With regard to geometric design elements, AASHTO’s A Policy on Geomet- ric Design of Highways and Streets (4), now in its 6th edition and often referred to as the Green Book, is the primary guide. For roadside elements—that area beyond the travel way and shoulder—it is AASHTO’s Roadside Design Guide (RDG) (5) that applies. For geometric design elements the Green Book provides suggested limiting values—either minimums or maximums depending on the specific design element, which in some cases can vary depending on the type of road, design speed, terrain, volume, and other factors. These values are to be considered guidelines and not strict requirements. Each state chapter three BackgrounD information on Project DeveloPment anD Design methoDs

10 FIGURE 1 Project development process. Source: AASHTO (2 ). is to exercise engineering judgment in selecting appropriate design values. The following statements in the foreword of the Green Book could apply to Practical Design: • This policy is therefore not intended to be a detailed design manual that could supersede the need for application of sound principles by the knowledgeable design professional. Suffi- cient flexibility is permitted to encourage independent designs tailored to particular situations. • Cost-effective design is also emphasized. The goal of cost- effective design is not merely to give priority to the most ben- eficial individual projects but to provide the most benefits to the highway system of which each project is part. In the RDG, the following similar points about the appli- cation of that guide are relevant to Practical Design: • If including the highest level of roadside design criteria is rou- tinely required in each highway design project—regardless of cost or safety effectiveness—it is likely that system-wide safety may stay static or even may be degraded. • Knowledgeable design, practically applied at the project level, offers the greatest potential for a continually improved trans- portation system. Design exceptions A design exception is a documented decision to design a high- way element or a segment of highway to design criteria that do not meet minimum values or ranges established for that high- way or project (6). For various reasons, it is not always practi- cal [emphasis added] or desirable that a project meet each and every design criteria and standard; some of these include: • Impacts to the natural environment, • Social or right-of-way impacts, • Preservation of historic or cultural resources, • Sensitivity to context, • Sensitivity to community values, and • Construction or right-of-way costs (6). Each state has its own policy, guidelines, and practices for when and how design exceptions will be used during proj- ect development and design. The state practices for design exceptions are documented in NCHRP Synthesis 316: Design Exception Practices (7). As explained in that synthesis, FHWA provides both regulatory (compulsory) and non regulatory direction on design exceptions. FHWA has established min- imum design criteria for projects on the National Highway System (NHS), which includes the entire Interstate system. These criteria are included in the AASHTO Green Book and in the AASHTO Policy on Design Standards—Interstate System (8). FHWA indicates that “[a]lthough all exceptions from accepted standards and policies should be justified and documented in some manner, the FHWA has established 13 controlling criteria requiring formal approval” (9). The fol- lowing 13 elements identified by FHWA in the Federal-Aid Policy Guide require formal design exceptions: 1. Design speed, 2. Lane width, 3. Shoulder width, 4. Bridge width, 5. Structural capacity, 6. Horizontal alignment, 7. Vertical alignment, 8. Grade, 9. Stopping sight distance, 10. Cross slope, 11. Superelevation, 12. Vertical clearance, and 13. Horizontal clearance (other than clear zone). context sensitive solutions FHWA defines CSS as “a collaborative, interdisciplinary approach that involves all stakeholders in providing a transpor- tation facility that fits its setting. It is an approach that leads to preserving and enhancing scenic, aesthetic, historic, commu- nity, and environmental resources, while improving or main- taining safety, mobility, and infrastructure conditions” (10). There are several key elements of CSS. First is the “context,” which is a broad description of a project’s physical, eco-

11 nomic, and social setting. The context may include the com- munity, ecological, aesthetic, and transportation conditions, as well as the political and policy environment. Another key element is the use of an interdisciplinary team—stakeholders with different backgrounds (community members, elected officials, interest groups, and affected local, state, and federal agencies) who work collaboratively to solve a common prob- lem. It puts project needs and both agency and community values on a level playing field and considers all tradeoffs in decision making. This process differs from traditional pro- cesses in that it considers a range of goals that extends beyond the transportation problem, including goals related to com- munity livability and sustainability, and seeks to identify and evaluate diverse objectives earlier in the process and with greater participation by those affected. A key tenant of CSS is recognizing the need to consider that transportation corridors may be jointly used by motorists, pedestrians, cyclists, and public transit vehicles. Many states have a policy on CSS and incorporate its princi- ples into their project development process. NCHRP Synthesis 373: Multi-Disciplinary Teams in Context-Sensitive Solutions (11) reported on state DOT CSS practices and NCHRP Report 480: A Guide to Best Practices for Achieving Context Sensitive Solutions (12) focuses on how state DOTs can incorporate CSS into transportation project development. More information about CSS can be found at: http://contextsensitivesolutions.org/ content/reading/context_sensitive_solutions_pri/. resurfacing, restoration, anD rehaBilitation Projects The program of resurfacing, restoration, and rehabilitation— commonly referred to as RRR or 3R—emerged out of the 1976 Federal-Aid Highway Act. The legislation permitted the use of federal aid to rehabilitate highways to extend their useful life without necessarily improving existing geo- metrics. These projects were not required to comply with the then current design standards, and would typically not change existing design dimensions. The 3Rs were defined as follows: • Resurfacing—Work to place additional layers of sur- facing on highway pavement, shoulders, and bridge decks, and necessary incidental work to extend the structural integrity of these features for a substantial time period. • Restoration—Work to return the pavement, shoulders, and bridges over a significant length of highway to an acceptable condition to ensure safety of operations for a substantial time period. This work may include the fol- lowing: grinding and repair of joints of portland cement concrete pavement; sealing of shoulders and pavement joints in conjunction with other work; placement of a skid-resistant surface treatment; correction of minor drainage conditions; and work to prepare a bridge deck for an overlay. • Rehabilitation—Work to remove and replace a major structural element of the highway to an acceptable condi- tion to extend the service life of a significant segment for a substantial period of years commensurate with the cost to construct. This may include the following: replacement of bridge deck, pavement, or shoulders without significant widening; recycling of pavement and shoulder materials; replacement of the individual bridge elements to correct a structural deficiency; and minor subgrade work incidental to other work. The federal regulatory requirements have changed over time. Current federal requirements are documented in FHWA’s Technical Advisory T5040.28 Developing Geometric Design Criteria and Processes for Non-Freeway RRR Projects (13). The technical advisory provides procedures, a process for developing 3R programs and projects, and design criteria for individual geometric elements. The technical advisory notes that the states’ 3R design criteria should address all 13 controlling geometric elements mentioned under Design Exceptions. In addition, guidance is provided on other design features such as pavement improvements including skid resistant surfaces and pavement edge drop-off remedia- tion, intersection improvements, and traffic controls and regulations. Nearly all states have a policy and design guidance for 3R projects; this was documented in 2011 in NCHRP Synthesis 417: Geometric Design Practices for Resurfacing, Restora- tion, and Rehabilitation (14). value engineering FHWA defines VE as a systematic process of project review and analysis during the concept and design phases by a multi-disciplinary team of individuals involved in the project conducted to provide recommendations for: 1. Providing the needed functions safely, reliably, effi- ciently, and at the lowest overall cost; 2. Improving the value and quality of the project; and 3. Reducing the time to complete the project (15) Although for many years VE has been recognized as a valuable tool for developing a cost-efficient project, it was the Federal-Aid Act of 1970 that made it a requirement for federal-aid projects. In late 1995, Congress passed the NHS Designation Act that included a provision requiring the secretary to establish a program that would require states to undertake a VE analysis for all federal-aid highway-funded projects with an estimated total cost of $25 million or more. Recent years have seen adjustments to the legislation and regulations established for VE. The current policy (16),

12 published on March 15, 2012, continues the $25 million threshold, but also requires VE for: • A bridge project with an estimated total cost of $20 mil- lion or more, and • Any other project designated by the secretary of trans- portation. State DOT VE practices, as of 2005, were documented in NCHRP Synthesis 352: Value Engineering Applications in Transportation (17). Among the many findings reported were: • VE is more effective and influential on the performance, quality, and cost of a project when performed relatively early in the development of the project schedule. • VE can effectively be integrated with or into other tech- nical management improvement approaches, such as asset management, RSA, contest sensitive design, and accelerated construction technology teams. flexiBle Design Flexible design refers to a design philosophy that permeates the entire project development process. There are no specific design criteria or guidelines associated with flexible design. In 1997, FHWA published Flexibility in Highway Design (18) to illustrate the flexibility available to designers within adopted state standards to tailor their designs to the particular situa- tions encountered in each highway project. It was prepared to demonstrate how agencies could accomplish the objectives of CSS within accepted design processes and criteria. Sub- sequently, in 2004, AASHTO published A Guide for Achiev- ing Flexibility in Highway Design (2). This guide promotes the incorporation of sensitive community and environmental issues into the design of highway facilities. It comprehensively addresses the overall project development process and offers specific examples of incorporating flexibility into the selection of specific design elements.