A Performance-Based Highway Geometric Design Process (2016)

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5 Highway engineering and design have evolved over the years in response to many factors, events, knowledge gained from both research and “trial and error,” and public policy initiatives. The following is a summary timetable of the evolution of design policy in the U.S. 2.1 Up to the 1940s Through the 1940s the U.S. highway system was primarily a two-lane rural system. The knowledge base for road design built on that of railroad engineering. Road design was a civil engineering discipline whose sub-discipline skills involved materials properties, structural design, drainage and hydraulics, construction means and methods, and basic physics and mechanics. There was little if any knowledge regarding the operation of vehicles, either individually or in traffic streams. The notion of human factors and the human element as an input to design was understood only in rudimentary terms. Indeed, a prevailing philosophy of highway engi- neers was that any road properly designed should be able to be driven safely by anyone and everyone. AASHO and the U.S. Bureau of Public Roads worked to develop and publish geometric design criteria. Early attempts to develop guidance related to traffic operations by necessity relied on hypothetical, simple rational models of presumed driver/vehicle behavior. The concept of stopping sight distance (SSD), for example, was based on a simple, rational concept that a driver ought to be able come to a full stop prior to striking an object in the road. An interesting sidebar regarding this early work has to do with the dimensions used for the object in the SSD model. Many designers to this day incorrectly believe that the 6-inch object used prior to 2001 had some functional meaning behind it. The very first application of this model to SSD criteria employed a 4-inch object height. That height was selected not because of its dimension, but rather based on a paper study of the cost effectiveness of constructing alignments to using a range of criteria, from 0 to over 1 foot. The 4-inch object was changed to a 6-inch object in later years when AASHO realized that the driver eye height in the vehicle fleet had dropped; but there did not appear to be a need to lengthen the design length of vertical curves. The originators of design policy relied on knowledge of the cost to build a road to make this policy choice, that being the only real knowledge available. An important policy decision at the federal level occurred in 1946. Congress voluntarily waived sovereign immunity. Up until that legislation it was not possible to bring a tort lawsuit against the federal government. State governments followed suit over the next 15 to 20 years. In waiving sovereign immunity a government takes on the responsibility to conduct its business, in the case here, designing and maintaining roads, in a responsible manner. C h a p t e r 2 The Evolution of Highway Design in the U.S.

6 a performance-Based highway Geometric Design process 2.2 The 1950s—The Technology of Highway Planning and Design Addresses Burgeoning Mobility Needs and National Public Policy Advances The 1950s saw rapid economic and population growth in the U.S.; Many cities grew significantly. The automobile became the predominant transportation mode. The U.S. vehicle fleet expanded tremendously, and traffic volumes increased on many major arterials. One of the most significant public policy initiatives in the country’s history was the passage of the 1956 act establishing a System of Interstate and Defense Highways. This initiative established both a funding stream as well as demand for high-type facilities across the country. Also in the 1950s the emergence of engineering documents and policy for use by the profession came into being. AASHO published the first “Blue Book”—A Policy on Geometric Design for Rural Highways—in 1954. In 1950 the first Highway Capacity Manual (HCM) was published, providing for the first time a knowledge base and methods for the evaluation of traffic operations. Also in the 1950s the science and technology around travel demand forecasting was invented. Travel and road building remained primarily rural, but the late 1950s and into the next decade saw the beginnings of major freeway and road building in urban areas. 2.3 The 1960s—The Growth of the Interstate System and Urban Transportation The 1960s saw an unprecedented construction of Interstate and other highways across the nation. These roads were for the most part on new alignment, including through major urban areas. Many of the first urban freeway projects had significant effects on cities, and created the first major controversies around roadway infrastructure. Highway agencies experienced in rural road design applied the same practices and approaches to urban freeways. They were (1) sized to meet theoretical demand and provide high-speed service—LOS C—for design year traffic; (2) designed to uniformly very high design speeds; and (3) designed and constructed as engineering infrastructure projects in which nontechnical stakeholders (that term did not emerge until decades later) had no role nor input. The Interstate system clearly played a major role in the mobility, quality of life, and economic growth of the U.S. Yet its emergence was not without problems. During the 1960s public concern over and interest in the adverse effects of public infrastructure projects (highways being one type) resulted in the first federal legislation around environmental protection. Other major events in the 1960s included the establishment by the highway community of the National Cooperative Highway Research Program (NCHRP) (in 1963) and an updated AASHO Blue Book (published in 1965). Thus began a program by states to jointly prioritize and fund research on important aspects of highway design, operation, and construction. As travel greatly increased, and high-speed Interstate highways were built and open to traffic, new problems emerged in road design. Traffic fatalities began to climb. By the late 1960s high- way deaths exceeded 53,000 annually. The highway death toll spurred congressional hearings which sought to understand the reasons for and causes of the increase in highway deaths. Among the contributing factors highlighted was the significant number of deaths attributed to vehicles running off the road and striking trees, fixed objects, ditches, and other roadside appurtenances. For the first time, the highway engineering profession became cognizant of the need to design the roadside to be “forgiving.” This insight changed the view of road designers and shaped future design policies.

the evolution of highway Design in the U.S. 7 2.4 The 1970s—Environmental Initiatives Drive National Transportation Policy and Programs The 1970s saw the maturation of the Interstate system, an explosion in traffic, and the onset of developing societal problems and issues associated with construction and operation of the highway system. The defining major policy initiative of the 1970s was passage of the National Environmental Policy Act (NEPA). Although NEPA was not aimed only at highway infrastructure, the widespread impacts of road building were clearly a contributor. With NEPA and other regulations and laws that followed, the highway project development process was forever changed. Road design and construction were no longer the purview of engineers and DOTs. The need to meet external stakeholder demands and requirements and address adverse impacts was central to the success of a project and agency program. In 1971 the landmark Overland Park decision by the U.S. Supreme Court codified judicial review over proposed actions of DOTs. DOTs had to learn how to develop projects to meet the new environmental regulations and laws. This required new skills and processes. It also required a cultural shift—the opening up of the highway engineering field to others not trained in highway engineering. The entire process became more complex; projects began to take longer to complete; and the costs of highway projects began to increase as the costs of meeting environmental requirements emerged. Also in the 1970s states began to experience a large increase in tort liability claims associated with allegations of negligence in their actions regarding the design and maintenance of their systems. The profession struggled with design process and risk management practices, including identifying the need to fully document their design decisions to support defense against tort claims. By the end of the decade another strong trend emerged—growing congestion in urban areas, often on freeways that were only 10 to 15 years old but operating at volumes above their design capacity. Some early Interstate projects constructed in the late 1950s and early 1960s began to show signs of wear and tear, leading to another looming problem—reconstruction of high-volume roads under traffic. In the 1970s AASHO produced its first design policy written for urban streets and arterials. The 1974 AASHO Red Book joined the Blue Book as the basis for road design in the U.S. A final important external event shaped road design and public policy for years to come. The oil embargo and sharp price increases in oil and gasoline that occurred in 1974 changed many things. Public policy shifted to fuel preservation and specifically regulations on fuel economy. Over the next 30 years motor vehicles would become more and more fuel efficient, resulting in a long-term reduction in the funding generated from federal fuel tax revenue. 2.5 The 1980s—Transportation Professionals Wrestle with Reconstruction Needs and Congestion as Emerging Issues The 1980s in many respects represented a watershed in the highway design profession. Urban- ization was in full force. DOT programs became more and more focused on urban road prob- lems. Much of the infrastructure constructed in the early 1960s showed need for rehabilitation or reconstruction. DOTs continued to struggle with how to address environmental requirements, both from a process and cost perspective. Growth in fuel tax revenue slowed, and for the first time since the Interstate era many agencies found themselves short of the necessary funds to meet program needs.

8 a performance-Based highway Geometric Design process In response to these trends the 1982 Surface Transportation Act mandated study of resur- facing, restoration, and rehabilitation (3R) projects. FHWA and AASHTO initiated studies of alternative design processes to address the newly recognized problem of infrastructure repair. This effort produced TRB Special Report 214: Designing Safer Roads (TRB 1987) and eventually policies by FHWA on defining 3R projects and enabling separate design criteria and approaches for these. AASHTO published the first Roadside Design Guide, a significant technical achieve- ment in which science-based knowledge was used and the concept of designing the roadside was established. The conflict between historic methods for roadway design and practical realities of demand and congestion in urban areas became apparent in more cities. Innovative design solutions— foremost among these being high-occupancy vehicle (HOV) lanes—emerged. In other locations such as the North Central Expressway in Dallas, design decisions were made to purposely limit corridor expansion based on available right-of-way and included new transit service as part of the overall solution. FHWA initiated research on the Interactive Highway Safety Design Model (IHSDM) in the late 1980s, beginning a process of integrating operational analysis into design. And AASHTO for the first time published a combined policy on geometric design covering both rural and urban facilities (A Policy on Geometric Design of Highways and Streets, the Green Book) in the same document. Finally, during the 1980s the incorporation of computer technology in many of the engineer- ing design functions took hold. The profession began a transition from a manual and slide-rule approach to the technical tasks of design, to one more automated. 2.6 The 1990s—Unsolved Problems of Congestion, Project Development, Community Sensitivity, and Funding Begin to Take Their Toll DOTs and cities continued to struggle with the costs and impacts of major projects. Boston’s Central Artery which began in the 1980s became a symbol to many of both the potential for change but also the complexity and cost of change. Even though NEPA was over 20 years old, many DOTs still had limited success in efficiently and effectively incorporating environmental and social issues into design development. The Intermodal Surface Transportation Efficiency Act (ISTEA) legislation of 1991 addressed pres- ervation of historic and scenic resources. But legislation was not enough. Perhaps the most significant movement to emerge in over 30 years did so in the early 1990s. Citizen groups, envi- ronmental and community activists, and local political leaders across the country became more assertive about their unhappiness with both the process and outcomes of their roadway projects. Context Sensitive Design (CSD) [which evolved to Context Sensitive Solutions (CSS)] was pro- moted as a new approach to transportation projects. CSD/CSS took on many attributes and directions. Some saw it as a way of addressing the inherently unattractive nature of road infrastructure. Others viewed it as a way to take over the road planning and design decision process from engineers and to local authorities and interests. FHWA and then AASHTO directed the discussion of CSS as more process oriented, with some technical advances. FHWA published Flexibility in Highway Design. NCHRP published NCHRP Report 480: A Guide to Best Practices for Achieving Context Sensitive Solutions. This document for the first time outlined the design dilemma posed by the application of design standards in the context of conflicts with property, environmental features, or other community values. CSS was promoted as being a process in which stakeholder interests were obtained in an organized

the evolution of highway Design in the U.S. 9 manner; designers were taught to understand flexibility that did exist within AASHTO policies, and the design process as one of making choices and trade-offs was codified. CSS remains somewhat misunderstood by many. Some DOTs embraced the CSS movement and adapted project delivery methods accordingly. Others gave it lip service or struggled with the philosophy behind it. From the perspective of AASHTO, though, and the history in many places of successful CSS projects, CSS became the expectation of DOT customers and as such has changed design delivery forever. The other major initiative in the 1990s that coincided with the CSS movement was a renewed interest and concern over highway fatalities. The AASHTO Strategic Highway Safety Plan, published in 1995 as a collaboration with many national partners, was a fundamental factor in shaping legislation and priorities. What is notable about this effort was that for the first time it represented an institutional awareness and understanding of the complexity of the road safety problem and multi-institutional responsibility for addressing it. The four Es—engineering, enforcement, education, and emergency medical services—were now understood to all play meaningful roles in both their own actions as well as in coordinating programs with each other. From the mid-1990s through the beginning of the next century, implementation of proven treat- ments and programs on a systemwide basis produced unprecedented reductions in road deaths. In large part because of this interest in safety, the highway engineering community through both AASHTO and FHWA made significant policy decisions in their research focus. AASHTO made two significant changes to the Green Book in the 1990s. The definition of design speed was changed to reflect continuing concerns over tort liability. Also, the SSD model was changed based on research from NCHRP Report 400 (Fambro et al. 1997). The object height of 6 inches was revised to 2 feet. This change was the first major design policy change that reduced rather than increased design requirements. Interestingly, many state DOTs were reluctant to embrace this change, choosing to retain the old policy as the basis for their design manuals, despite the fact that it would cost them more. The leadership in such states expressed a concern that they wanted to “be more conservative” and use the old SSD model. By the 1990s highway engineering design had become fully automated. The tasks of comput- ing cross sectional and alignment values became much less onerous, less costly, and less prone to engineering error. 2.7 The 2000s to the Present Day—The Need for a New Highway Design Paradigm Is Recognized The 21st century has seen the continuation of trends earlier established and the emergence of new challenges. The continuation of fuel efficiency placed more severe, permanent limitations on funding for road improvements. Aging infrastructure became the primary problem facing DOTs; the I-35W river bridge collapse was emblematic of the problem, but it was by no means the only example. DOTs also came under considerable pressure to expand their programs to explicitly include pedestrian and bicycle infrastructure. The severe financial pressures led to innovative approaches, both in project delivery and funding. Regarding the former, the Missouri DOT created the concept of “practical design.” The Washington DOT, in response to the needs of funding many major corridor programs and dealing with aging infrastructure on the rural system, fundamentally changed its programming and project design approach with its innovative “design matrices.” Other states followed the lead and have experi- mented with different project design approaches. During this time design-build as an alternative delivery approach emerged. Among the benefits that states have experienced is the innovation in design and construction that enabled projects to be built at lower costs and more quickly.

10 a performance-Based highway Geometric Design process In the view of most DOT leaders, funding limitations to meet program needs have become permanent. Part of the solution to this has been emergence of P3s (public/private partnerships) and tolling. This trend does not directly influence the design process, but it does reinforce the view that DOTs are being expected to produce maximum measurable value for their investments. Indeed, during the 2000s the importance of performance measurement and asset management to program success is a response to these pressures. As projects and programs underwent greater scrutiny and the environmental process became more complex, concerns about project delivery time increased during the 2000s. Many major projects took 5 to 10 years or even more from initial planning to construction. Costs increased as well. Environmental streamlining emerged as an important initiative. Perhaps the most significant long-term innovation during the 2000s was the completion of a 10-year effort to develop the first ever Highway Safety Manual (HSM). This document is now being implemented by state DOTs. The implications of the HSM with respect to DOT programs and design development in particular are clear. Highway engineers now for the first time have a knowledge base and methodology for developing an objective analysis of the safety performance of their designs. 2.8 Recent Advances in Highway Design 2.8.1 Introduction The AASHTO Green Book (AASHTO 2011a) is fundamentally a collection of quantitative geometric design criteria and qualitative design guidance that does not purport to represent any particular design process. The essentially unstated concept in the Green Book is that, if a project is designed in accordance with Green Book criteria and Green Book guidance, the completed project will operate safely and efficiently. Federal policy has institutionalized design criteria as controlling criteria for geometric design as requiring design exceptions if the criteria are not met for new construction or reconstruction projects on National Highway System (NHS) routes and for rehabilitation projects on Interstate freeways. State policies may require design exceptions not only for the controlling criteria identified by FHWA, but for other geometric design criteria as well. The current geometric design process, based on the AASHTO Green Book and state highway agency design manuals together with the design exception process, or something like it, was likely necessary as a design control in the past, when the operational, particularly safety, effects of geometric design criteria were poorly understood. In the past 25 years, there has been an increas- ing industry movement toward greater flexibility in design to help projects meet the needs of multiple stakeholders. This flexibility has become easier to justify on a project-by-project basis as knowledge about previously unknown traffic operational and safety effects has advanced. Publications that document the need for flexibility, and the extent of flexibility that is achievable in the current design process, include the AASHTO A Guide for Achieving Flexibility in Highway Design (AASHTO 2004) and the FHWA Flexibility in Highway Design (FHWA 1997). As the range of stakeholder views about highway projects and the industry movement toward flexibility have expanded, a number of alternative design concepts have become part of design practice. These alternative concepts include: • The complete streets concept, which focuses on creating roadways and related infrastructure that provide safe travel for all users. • The concept of CSD, better known as CSS, places priority on assuring that highway projects fit the context of the area through which they pass, puts project needs as well as the values of

the evolution of highway Design in the U.S. 11 the highway agency and community on a level playing field, and considers all trade-offs in decision making. • The concept of performance-based design incorporates a design process that considers explicit consideration of performance measures, typically operational and safety performance measures. • The concept of practical design focuses on addressing only those improvements that are needed and eliminating those improvements that are not absolutely essential, thereby reducing the overall cost of a project. • The design matrix approach includes three levels of design for highway projects: basic, modified, and full design levels. • The safe systems approach takes a holistic approach in that the responsibility for road safety is shared between all facets of the transportation system (i.e., roadway infrastructure, roadway users, and vehicles). • The concept of travel time reliability focuses on designing a roadway in such a way that maximizes the travel time reliability of the roadway. • The concept of value engineering (VE) is a systematic process of project review and analysis by a multidisciplinary team to provide recommendations for improving the value and quality of the project. • The concept of designing for 3R projects includes a set of geometric design criteria that are less restrictive than the geometric design criteria in use for new construction and reconstruction. • The concept of Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT ≤ 400) (AASHTO 2001) recognizes that VLVLR represents a different design environment than higher- volume roads. All of these concepts profess to consider a broad range of design issues, but each concept has been advocated by interest groups or adopted by highway agencies with specific priorities in mind. The advocates of each of these alternative concepts recognize the need to consider competing viewpoints in the design of a project, and likely consider themselves to be seeking project designs that consider and balance all competing stakeholder goals and interests, but their choice of the alternative concept they advocate often tells something about the factors to which they assign a high priority. The stated goal of the complete streets concept is to consider all transportation modes in the design of urban and suburban arterials; most advocates of complete streets emphasize explicit consideration of bicycle and pedestrian needs. The stated goal of CSS is to assure that each project is designed in a manner consistent with the context of the roadway; most advocates of CSD advocate strong consideration of community, neighborhood, and/or environmental values. The stated goal of performance-based design is to explicitly consider operation and safety perfor- mance measures in the design process and, potentially, to design to achieve specific operation and/or safety goals for each project. The stated goal of practical design is, where appropriate, to relax specific design criteria to minimize project costs, consistent with achieving other stated goals; most advocates of practical design seek to take maximum advantage of design flexibility in reducing costs. The stated goal of the safe systems approach is to design each project so that motorists will choose to travel at speeds that the designers consider appropriate to the crash risks present on the roadway; advocates of the safe systems approach typically assign a high priority to the consideration of safety performance measures. The goal of travel time reliability is to make travel time more consistent, and thus reduce day-to-day variations in travel times on a given section of road; advocates of travel time reliability are typically seeking designs that can reduce the potential impact of non-recurrent congestion on travel times. Value engineering seeks to improve the value of designs, by modifying any aspect of the design that would result in an increase in value; advocates of VE have similar goals to advocates of practical design, but potentially seek not only the same (or better) project performance at lower cost, but also better project performance, even at somewhat higher cost.

12 a performance-Based highway Geometric Design process Highway agency criteria for design of 3R projects on nonfreeway facilities and the AASHTO Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT ≤ 400) (AASHTO 2001) are both examples of practical design and the application of design flexibility, based on risk assessment, that seeks to achieve equal (or, at least, acceptable) performance to that achieved by full AASHTO Green Book design criteria at lower cost. All of the alternative concepts have useful features that should be considered in developing a revised geometric design process. Yet, none of these concepts by themselves, are a complete and sufficient process for identifying and considering all factors relevant to design decisions. Each of these alternative concepts is reviewed below with the intention of identifying features of each concept that will ideally become part of a revised geometric design process. 2.8.1.1 Complete Streets Concept For years, the objective of designing a roadway was to move as many vehicles (and without emphasis on all road users including pedestrians and bicyclists) as possible, as efficiently as pos- sible, from point A to point B. This was the objective whether one was designing a freeway or a city street. Today, however, the objective of designing a roadway—particularly one with mul- tiple user types—has shifted toward providing for the safe mobility of all travelers, not just those in motor vehicles. This concept has become referred to as “complete streets.” According to the National Complete Streets Coalition, complete streets are designed to enable pedestrians, bicyclists, motorists, transit users, and travelers of all ages and abilities to move along the street safely. Although the guiding principle for complete streets is to create roadways and related infra- structure that provide safe travel for all users, each complete street has to be customized to the characteristics of the area the street serves. Traffic calming techniques are sometimes used to encourage lower speeds to increase safety. A complete street also has to accommodate the needs and expectations of the travelers who want to access or pass through the surrounding neighborhood, community, or region. According to the National Complete Streets Coalition, typical elements that make up a complete street include: • Sidewalks; • Bicycle lanes (or wide, paved shoulders); • Shared-use paths; • Designated bus lanes; • Safe and accessible transit stops; and • Frequent and safe crossings for pedestrians, including median islands, accessible pedestrian signals, and curb extensions. Certainly, a design for a complete street in a rural area will look quite different from one in an urban or suburban area. For example, a complete street in a rural area could involve providing wide shoulders or a separate multi-use path instead of sidewalks. The common denominator, however, is balancing safety and convenience for everyone using the road. 2.8.1.2 CSS The concept of CSS has been evolving in the transportation industry since the 1969 NEPA of required transportation agencies to consider the possible adverse effects of transportation projects on the environment. The CSS concept gained significant momentum in 1998 when the AASHTO and FHWA jointly sponsored the “Thinking Beyond the Pavement” national conference, which generated the first working definition of CSD. Since that conference, CSD has evolved into CSS, which is defined as:

the evolution of highway Design in the U.S. 13 Context sensitive solutions (CSS) is a collaborative, interdisciplinary approach that involves all stake- holders in providing a transportation facility that fits its setting. It is an approach that leads to preserving and enhancing scenic, aesthetic, historic, community, and environmental resources, while improving or maintaining safety, mobility, and infrastructure conditions. (Joint AASHTO/FHWA 2007) The CSS concept places priority on assuring that highway projects fit the context of the area through which they pass, particularly with respect to neighborhood, community, and environ- mental concerns. A CSS approach puts project needs as well as the values of the highway agency and community on a level playing field and considers all trade-offs in decision making. A CSS approach is guided by four core principles: • Strive toward a shared stakeholder vision to provide a basis for decisions; • Demonstrate a comprehensive understanding of contexts; • Foster continuing communication and collaboration to achieve consensus; and • Exercise flexibility and creativity to shape effective transportation solutions, while preserving and enhancing community and natural environments. NCHRP Report 480: A Guide to Best Practices for Achieving Context Sensitive Solutions was developed by Neuman et al. (2002) and demonstrates how transportation agencies can incorporate context sensitivity into their transportation project development work. The guide is applicable to a wide variety of projects that transportation agencies routinely encounter. One of the key strengths of a CSS approach is its applicability to all of the roles found within a transportation agency, including project managers, highway engineers, environmental specialists, public involve- ment specialists, senior managers, and transportation agency administrators. While each role brings a different point of view to the table, all of the roles are critical to the success of trans- portation improvements. NCHRP Report 480 was designed to reflect each of these different perspectives. 2.8.1.3 Performance-Based Design Performance-based design incorporates a design process that considers explicit consideration of performance measures, typically operational and safety performance measures. In performance- based design, each design decision should be explicitly assessed in terms of its potential impact on operations and safety. NCHRP Report 785: Performance-Based Analysis of Geometric Design of Highways and Streets (Ray et al. 2014) provides a principles-focused approach that looks at the outcomes of design decisions as the primary measure of design effectiveness. Performance-based design is consistent with the HSM (AASHTO 2010) goal of moving away from design for nominal safety (i.e., meeting specific geometric design criteria) toward sub- stantive safety (i.e., meeting explicit performance criteria). Carried to its logical conclusion, performance-based design could have the goal of meeting specific operational and safety targets established by the highway agency for each project. Since the development of the level-of-service concept in the 1965 HCM, geometric design has always been performance-based with respect to operations. Only with the publication of the first edition of the HSM in 2010 has it been possible for geometric design to be truly performance-based with respect to safety for at least some design criteria. As new capabilities are added to the HSM over time, it will become increasingly possible for design of all geometric criteria for all project types to be performance based. The HCM (TRB 2010) serves as a traffic operational-performance evaluation tool for performance-based design. The most common traffic operational-performance measure is the LOS determined with HCM procedures. Levels of service, represented by levels A (uncongested) through F (oversaturated), are based on different performance measures (known in the HCM as service measures) for each facility type. The performance measures used as service measures in the current HCM are shown in Table 1.

14 a performance-Based highway Geometric Design process Highway agencies generally set LOS targets for each project. Table 2, based on the Green Book Table 2-5, suggests specific LOS targets for projects by functional class and terrain. However, highway agencies can adjust these targets for all projects or for specific projects within their jurisdiction. FHWA has recently published a memorandum clarifying that there are no regula- tions or policies that require minimum LOS values for projects on the NHS, http://www.fhwa. dot.gov/design/standards/160506.cfm. The publication of the first edition of the HSM in 2010 (AASHTO 2010) gave highway agen- cies for the first time a broadly based tool for performance-based safety analysis. The HSM Part C procedures can be used to estimate the expected long-term crash frequencies and crash severity/crash type distributions for a range of project types. HSM Part C provides crash predic- tion models for rural two-lane highways, rural multi-lane highways, and urban and suburban arterials. The results of NCHRP Project 17-45 have added crash prediction models for freeways, interchange ramps, and ramp terminals. HSM procedures are provided to combine crash pre- dictions from the HSM Part C models with observed crash history data to obtain the best avail- able estimate of long-term crash frequency for a particular roadway segment or intersection. The current HSM procedures are reasonably comprehensive (see the list in Table 3 of geometric design elements currently included), but do not necessarily address every geometric design ele- ment of potential interest to designers. Research is continuing and more geometric design ele- ments will likely be added to the HSM procedures over time. The HSM models have the following general form, which incorporates safety performance functions (SPFs), crash modification factors (CMFs), and calibration factors: N N CMF CMF . . . CMF Cpredicted spfx 1x 2x yx x( )= × × × × × Where: Npredicted = Predicted average crash frequency for a specific year for site type x; Nspfx = Predicted average crash frequency determined for base conditions of the SPF devel- oped for site type x; Facility Type HCM Chapter Performance Measure(s) Used as the HCM Service Measure Rural Two-Lane Highways 15 Percent time spent following average travel speed Rural Multilane and Suburban Highways 14 Traffic density Urban Streets 16–17 Average Travel Speed Freeways 10–13 Traffic density Signalized Intersections 18 Delay Unsignalized Intersection 19–21 Delay Table 1. Performance measures used to determine LOS in the HCM. Functional Class Appropriate LOS for Specified Combinations of Area and Terrain Type Freeway Arterial Collector Local Rural Level B B C D Rural Rolling B B C D Rural Mountainous C C D D Urban and Suburban C or D C or D D D Table 2. Guidelines for selection of design LOS in the Green Book.

the evolution of highway Design in the U.S. 15 CMF1x = Crash modification factors specific to site type x and specific geometric design and traffic control features y; and Cx = Calibration factor to adjust SPF for local conditions for site type x. The CMFs used in the crash prediction models take a variety of forms. As an example, the following equations (Table 4), illustrated in Figure 1, show how the value of the CMF for lane width on rural two-lane highways is determined. A performance-based design process involves, at a minimum, estimating the operational and safety effects of each design decision for which it is feasible to make such estimates with avail- able tools and to consider those operational and safety estimates explicitly in making geometric design decisions. Typically, many factors other than operations and safety are considered in geometric design decisions, so operations and safety will not necessarily be the deciding factors for all geometric design decisions in all projects, but clearly designers recognize operations and safety as important decision factors. A performance-based design process, with goals based on both operational and safety targets, is now feasible for many projects. The current state of practice already includes a performance-based design process with goals based on traffic operational (i.e., LOS) targets. Lane width Shoulder width Horizontal curve length Horizontal curve radius Superelevation and presence or absence of spiral transitions Grades Driveway density Passing lanes Two-way left-turn lanes Intersection skew angle Median width Right-turn lane Left-turn lane Table 3. Geometric design elements in current HSM chapters. Note: The collision types related to lane width to which this CMF applies include single-vehicle run-off-the-road and multiple-vehicle head-on, opposite-direction sideswipe, and same-direction sideswipe crashes. Average Annual Daily Traffic (AADT) (vehicles per day) Lane Width <400 400 to 2000 >2000 9 feet or less 1.05 1.05+2.81×10-4(AADT-400) 1.50 10 feet 1.02 1.02+1.75×10-4(AADT-400) 1.30 11 feet 1.01 1.01+2.5×10-5(AADT-400) 1.05 12 feet or more 1.00 1.00 1.00 Table 4. CMF for lane width on roadway segments (CMFra).

16 a performance-Based highway Geometric Design process A performance-based design process with goals based on safety targets (i.e., specific crash fre- quencies either for expected total crashes or expected crashes by severity level) is now feasible, although it does not appear that such a process has yet been adopted. One disadvantage of such a process is that highway agencies might be reluctant to specify explicit crash frequency targets for a project, because it may leave them open to tort liability actions for crashes that occur at a project site where actual crash experience exceeds the target levels; in such a case, plaintiffs might argue that the design selected by the highway agency was inappropriate since the target crash frequency was exceeded. A more workable alternative might involve establishing design categories for projects, where the description of each design category might include a range of expected crash frequencies. 2.8.1.4 Practical Design The concept of “practical design” focuses on doing everything well instead of a few things perfectly. The concept was first developed within the Missouri Department of Transportation (MoDOT) amidst serious funding shortfalls and rising construction costs. MoDOT’s senior man- agement decided that, while the negative economic conditions were completely beyond MoDOT’s control, they were not willing to deliver anything less to the public than they had promised. As part of MoDOT’s practical design process, they critically review projects to establish reduced-cost scope and road geometry based on needs and not standards. That is, those improve- ments that are really needed are included in projects, and those improvements that could be con- sidered unnecessary are eliminated. In essence, MoDOT’s practical design process aims toward “fewer spots of perfection and more good projects that make a great system” (McGee 2013). In Implementation Guide: Practical Design, Meeting Our Customer’s Needs (MoDOT, nd), MoDOT provides primary design guidance for 29 areas including type of facility, geometric design elements, pavements, structures, roadside safety, and miscellaneous. The guidelines provided in that document allow for flexibility in the selection of the specific design value. Figure 1. CMF for lane width on roadway segments.

the evolution of highway Design in the U.S. 17 MoDOT is not the only state DOT faced with many demands—such as maintenance, expanding infrastructure, and improving safety—and having to meet these demands with limited financial resources. In an attempt to deliver a highway system that meets the needs of taxpayers yet still fits within a very limited budget, several highway agencies have adopted the concept of practical design. The Kentucky Transportation Cabinet (KYTC) has approached this program from a somewhat different perspective through its “Practical Solutions” initiative, where the philosophy of build- ing reduced-cost projects is emphasized using the existing condition as the baseline design and thus achieving a positive outcome with project improvements beyond the existing conditions. In addition to Missouri and Kentucky, four other states have adopted practical design policies and procedures. These include Idaho, Kansas, Oregon, and Utah. 2.8.1.5 The Design Matrix Approach The Washington Department of Transportation (WSDOT) developed its own way of imple- menting practical design. WSDOT established three levels of design for highway projects: basic, modified, and full—known as a design matrix. The design matrices were used to identify the design level, as defined below, for a project and the associated processes for allowing design variances. • Basic Design Level—preserves pavement structures, extends pavement service life, and main- tains safety highway operations. • Modified Design Level—preserves and improves existing road geometry, safety, and opera- tional elements. • Full Design Level—improves road geometry, safety, and operational elements. The design matrices addressed the majority of preservation and improvement projects and focused on those design elements that were of greatest concern in project development. 2.8.1.6 The Safe System Approach Australia and New Zealand, as well as much of the European Union, have adopted the safe system approach to road safety improvement. The safe system approach takes a holistic view in that the responsibility for road safety is shared between all facets of the transportation system (i.e., roadway infrastructure, roadway users, and vehicles). The elements of this approach are: • Safe Roads and Roadsides—roads that provide an environment for road users to make informed and timely decisions on the paths of travel, preventing crashes from happening where pos- sible, encouraging appropriate travel speeds, and that are forgiving, not penalizing road users with death or serious injury if they make a mistake. • Safe Speeds—setting speeds that are consistent with the functional classification of the road and appropriate for the road environment and road users’ circumstances such that a person should survive the most likely type of crash should one occur. • Safer Vehicles—vehicles that protect occupants and road users should a crash occur. • Road users who are being alert and compliant. Under a safe system, crashes should be prevented from happening where possible. Where not possible, the travel speed should be such that a person should survive the most likely type of crash to occur. The speeds, above which the chances of surviving a crash substantially decrease are currently: • 70 km/h (45 mph) for head-on crashes, • 50 km/h (30 mph) for sideswipe crashes,

18 a performance-Based highway Geometric Design process • 40 km/h (25 mph) for fixed-object crashes, and • 30 km/h (20 mph) for crashes involving a pedestrian or bicyclist. 2.8.1.7 Travel Time Reliability As noted in the discussion of performance-based design in Section 2.8.1.3, the accepted mea- sure of traffic operational performance for highway projects is the LOS which, in turn, is derived from specific operational-performance measures for specific facility types, as indicated in Table 1. In recent years, highway agencies have begun to consider an alternative method of characterizing the traffic operational performance of highway facilities based not only on their LOS, but also on how consistently that LOS is provided from hour to hour and day to day over a period of a year or more. That consistency in meeting traffic operational expectations is referred to as travel time reliability. Travel time is influenced by recurrent congestion, which occurs in hourly traffic patterns that typically repeat themselves from day to day. Travel time reliability is strongly influenced by nonrecurrent congestion which results in traffic delays from factors other than the typical hourly traffic patterns. Key sources of nonrecurrent congestion include: • Traffic incidents, • Special events, • Work zones, • Traffic control devices, • Demand fluctuations, and • Weather. The concept of travel time reliability has been most extensively developed in the second Strategic Highway Research Program (SHRP 2) reliability research effort. Specifically, SHRP 2 Project L07, “Identification and Evaluation of Design Treatments to Reduce Nonrecurrent Con- gestion,” developed a tool to assist highway agencies in selecting geometric design treatments to reduce nonrecurrent congestion and, therefore, increase travel time reliability (Potts et al. 2013) (http://www.trb.org/main/blurbs/170653.aspx). This Project L07 tool could enable consider- ation of travel time reliability to become a routine part of the geometric design process. SHRP 2 Project L07 has documented that traffic congestion has effects on safety as well as traffic operations. Figure 2 illustrates the typical variation of crash frequency, by crash severity level, with traffic operational LOS. The figure illustrates that crash frequencies increase with conges- tion over the congestion range from LOS C to LOS F. This implies, conversely, that safety can be improved by improving traffic operations in the range from LOS F to LOS C. 2.8.1.8 The VE Concept Value engineering is typically implemented in geometric design once the project design is nearly complete and ready for a design review. A VE review is typically performed by engineers other than those who designed the project and their role is to look for opportunities to increase the project’s value. Value can be defined in terms of any performance measure for the design, including project cost. VE seeks to identify changes to the initial design that will either provide the same (or better) performance at less cost, will provide better performance for the same cost, or will, in some cases, provide better performance for additional cost. In its application to highway projects, and highway design in particular, VE has often trans- lated to a revisiting of design standards or criteria applied to a project. VE practitioners question assumptions behind the design standards as to their relevance or appropriateness given their impacts on project costs. VE also questions the lack of linking design standard dimensions to measures of value such as travel time, delay, or crash cost savings.

the evolution of highway Design in the U.S. 19 Given this approach, VE can be seen as a variation of performance-based design and practical design. Value engineering is, by definition, performance-based, because the value of a project cannot be assessed without one or more performance measures. The performance measures can represent safety, traffic operations, project cost, or any other attribute that stakeholders value. 2.8.1.9 Design of 3R Projects Since the 1980s, fewer new roads have been built, thus shifting the emphasis of highway agencies to reconstructing or rehabilitating the existing highway system. The aging of the high- way system, together with fiscal constraints, are placing increased pressures on highway agencies to maintain the highway system in a cost-effective manner and are, thus, creating greater needs for 3R projects. Geometric design criteria have historically been established by AASHTO policies, which apply not only to new construction projects but also to reconstruction projects. In 1977, AASHTO proposed a set of geometric design criteria for 3R projects (the “purple pamphlet”) that were less restrictive than the geometric design criteria in use for new construction and reconstruction (AASHTO 1977). This proposal began a storm of criticism from safety advocates who wanted all 3R projects brought up to full new construction criteria in the name of safety. One of the contro- versies was whether resurfacing of 3R projects without accompanying geometric improvements resulted in speed increases that, in turn, increased crash rates. Congress held hearings on this issue in 1981 and, as a result, the Surface Transportation Assistance Act of 1982 mandated a study of the cost effectiveness of geometric design standards and the development of minimum standards for 3R projects on roads other than freeways. The result of this congressional mandate was a formation of study committee and the publica- tion in 1987 of TRB Special Report 214: Designing Safer Roads: Practices for Resurfacing, Restoration, and Rehabilitation Projects (TRB 1987). Special Report 214 proposed geometric criteria for 3R proj- ects that have become widely accepted. TRB Special Report 214 was accompanied by TRB State of the Art Report 6 (Crump 1987), which presented seven resource papers that documented the Crash rates (O = Observed; Line = Predicted): Total PDO FI Cr as he s pe r M VM T 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 Traffic density (pc/mi/ln) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 Figure 2. Typical observed and predicted total, fatal and injury (FI), and property damage only (PDO) crash rates vs. traffic density (Potts et al. 2013). (MVMT = million vehicle miles traveled: pc/mi/ln = passenger cars/per mile/per lane.)

20 a performance-Based highway Geometric Design process then current state of knowledge on lane width, shoulder width, and shoulder type (Zegeer and Deacon 1987); bridge width (Mak 1987); pavement edge drop-offs (Glennon 1987a); roadway alignment (Glennon 1987b); sight distance (Glennon 1987c); pavement resurfacing (Cleveland 1987); and the potential impact of future changes in the vehicle fleet (Glauz 1987). There have been many changes in both the state of knowledge and highway agency policies since the publication of TRB Special Report 214 in 1987. These include: • Five updates to the AASHTO Green Book (in 1990, 1994, 2001, 2004, and 2011); • Establishment of agreements between FHWA and a number of state highway agencies on 3R design policies; • Publication of the AASHTO Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT ≤ 400) in 2001 (AASHTO 2001); • Research on the effect of pavement resurfacing on traffic speed in NCHRP Report 486 in 2003 (Harwood et al. 2003); • Completion of the Resurfacing Safety Resource Allocation Program (RSRAP) in NCHRP Report 486 in 2003 (Harwood et al. 2003); • Publication of the latest safety knowledge in the first edition AASHTO HSM in 2010 (AASHTO 2010); • Completion of additional safety research leading toward a second edition of the HSM; and • Updates of the TRB HCM in 2000 and 2010 (TRB 2010). Research in NCHRP Project 15-50 is developing an update to the 3R design guidelines in TRB Special Report 214, which was written 25 year ago. It appears that, to meet the current needs of highway agencies, the updated guidelines should not simply address geometric design criteria, but should provide a cost-effectiveness analysis approach to assist agencies with geometric design decisions, together with tools to implement that approach. Such a cost-effectiveness tool could potentially be created by updating the spreadsheet-based RSRAP tool from NCHRP Report 486 (Harwood et al. 2003), developed more than 10 years ago. 2.8.1.10 The AASHTO Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT ≤ 400) AASHTO published the Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT ≤ 400) (AASHTO 2001), referred to here as the VLVLR guidelines, in 2001. These guidelines were written as part of NCHRP Project 20-7(108), based on risk assessment research performed in NCHRP Project 20-7(75). The guidelines were developed in recognition that VLVLR repre- sent a different design environment than higher-volume roads, which are generally designed in accordance with the AASHTO Green Book (AASHTO 2004, FHWA 1997, AASHTO 2001). Such roads represent a significant portion of many agencies’ road networks, and their construction and maintenance can require major portions of their operating budgets. The design environment for VLVLR is distinct in that the lower average daily traffic design volumes [400 veh/day (vpd) or less] translate to a much lower risk profile than other roads with higher traffic volumes. In addition, local roads (except those in recreational areas) by definition serve a driver population primarily made up of repeat drivers who are familiar with the roads. The guidelines also address VLVLR with other driver populations, including recreational roads (which are more likely to serve unfamiliar drivers) and resource recovery roads (such as roads under the jurisdiction of the U.S. Forest Service) used primarily by professional drivers in larger design vehicles. Finally, the current VLVLR guidelines state that the guidelines may be applied not only to VLVLR, but also to very low-volume roads functionally classified as collectors, if they serve traffic volumes of 400 vehicles per day or less and serve a driver population that consists primarily of drivers familiar with the road in question.

the evolution of highway Design in the U.S. 21 With the above in mind, development of the AASHTO VLVLR guidelines presented geomet- ric design criteria for many specific design elements, applicable to new construction or recon- struction projects that are less restrictive, and thus less costly to implement, than the design criteria applicable to higher-volume roads, as presented in the Green Book. These less restrictive design criteria were justified through a risk assessment conducted in NCHRP Project 20-07(75), “Geometric and Roadside Safety for Very Low Volume Roads,” which reflected the very low crash frequency risk expected on very low-volume roads (Neuman 1998). Furthermore, the guidelines introduced the concept that geometric design changes to existing VLVLR may be essential only where documented crash patterns indicate a safety performance benefit associated with such changes. Where no crash pattern associated with a specific geometric feature or element exists, the guidelines enable highway agencies to leave the road geometry unchanged when undergoing infrastructure-related reconstruction. This flexibility in the guidelines allows agencies to avoid investing limited highway funds in geometric design changes intended to improve safety unless there is evidence of a likely documentable safety benefit from the improvement. As traffic volume is the most basic and strongest indicator of crash risk, benefits from geometric improvements are much more likely achievable on higher-volume roads than on very low-volume roads. Thus, the design guidelines for existing VLVLR provide great flexibility to highway agencies and intro- duce a strong sense of “if it ain’t broke, don’t fix it,” with crash history data guiding decisions as to whether geometric design changes should be considered. Both the research philosophy and the adoption of the VLVLR guidelines represent the first major change in highway design criteria to be more “context-sensitive” and directly responsive to principles of cost effectiveness as determined by the relationship of traffic volume to trans- portation value. 2.8.1.11 Summary of Alternative Concepts for Consideration There has been an increasing movement toward greater flexibility in design to help trans- portation projects meet the needs of multiple stakeholders. As the range of stakeholder views about highway projects and the industry movement toward flexibility have expanded, a number of alternative design concepts have become part of design practice. These alternative concepts include: • The complete streets concept, • The concept of CSS, • The concept of performance-based design, • The concept of practical design, • The design matrix approach, • The safe systems approach, • The concept of travel time reliability, • The concept of VE, • The concept of Designing for 3R Projects, and • The concept of Designing for VLVLR (≤ 400 ADT). Each of these alternative concepts has useful features that should be considered in developing a revised geometric design process. Yet, none of these concepts are, by themselves, a complete and sufficient process for identifying and considering all factors relevant to design decisions. In total though, these alternative concepts reveal that the following are important lessons to a revised geometric design process: • Roads serve more than just motor vehicles, • Road design involves many different disciplines, • Context matters and it varies,

22 a performance-Based highway Geometric Design process • Performance (operational, safety) is important, • Performance may have many dimensions, • Safety performance should focus on elimination or mitigation of severe crashes, • Speed and crash severity are closely linked, • Existing roads with known problems are different from new roads, • Traditional design approaches are believed by professionals to yield suboptimal results, • Focusing on identifying and addressing the problem(s) should be central to developing design solutions, and • Safety risk and cost effectiveness are related to traffic volume. These lessons are also common among multiple alternative concepts. Table 5 presents a matrix that demonstrates how the various concepts emphasize each of these lessons. The design matrix approach developed by WSDOT appears to hold promise as a new frame- work for organizing geometric design. 2.8.2 History and Evolution of the Highway Industry Much has changed from the 1940s to the present. Although the highway system is still pre- dominantly rural, the majority of trip-making occurs in urban areas. From the 1950s up until the 1970s, the task of planning, design, and construction of roads was a highway engineering Important Insights for the Geometric Design Process Alternative Design Processes and Initiatives Co m pl et e St re et s CS D Pe rfo rm an ce - B as ed D es ig n Pr ac tic al D es ig n D es ig n M at rix Sa fe S ys te m s Tr av el T im e R el ia bi lit y V al ue En gi ne er in g D es ig ni ng fo r 3R D es ig ni ng fo r V LV LR Sy ste m ic S af et y Roads serve more than just motor vehicles Road design involves many different disciplines Context matters and it varies Performance (operational, safety) is important Performance may have many dimensions Safety performance should focus on elimination or mitigation of severe crashes Speed and crash severity are closely linked Existing roads with known problems are different from new roads Traditional design approaches are believed by professionals to yield suboptimal results Focusing on identifying and addressing the problem(s) should be central to developing design solutions Safety risk and cost effectiveness are related to traffic volume Note: Fully applies Partially applies Table 5. Overlap of alternative design concepts.

the evolution of highway Design in the U.S. 23 problem that DOTs undertook with little outside involvement. Resources were sufficient, with strong public support for road construction. The combination of environmental sensitivities, greater public interest in infrastructure, and urbanization of the industry produced changes in the types of projects and approaches to design. Throughout the past 60 years DOTs and the AASHTO community have invested in research and adapted in many ways to these changes; but in many ways change has not occurred to the extent needed. The mindset of designers and design processes continues to be “rural-oriented” and is not sufficiently adapted to the unique, multimodal urban environment. Such a mindset is often characterized by the mantra “more is better.” In an era and context in which funds are adequate, additional right-of-way readily available, and adverse consequences de minimis, this mindset has been considered the appropriate, conservative approach to highway design. This design process, originally developed when most road design projects were new rural alignments on newly acquired right-of-way, has been slow to acknowledge these important fundamental differences: • In many areas, and for many agencies, new roads are a tiny or negligible part of their overall program. The vast majority of projects are reconstruction of existing roads on existing right- of-way, which are unique in their design challenges. • There was considerable growth in knowledge over the past 20 years on the safety and opera- tional effects of road design dimensions and variables; much more and deeper knowledge than existed when the original design policies were written and updated. Such knowledge grows every year and enhances the understanding of what impacts design decisions can have. • Design criteria for the most part are fundamentally unchanged in their basic forms from the early days of their development. Despite recent research and some revisions to design policy, the basic models underpinning much of highway engineering remain overly simplistic, insen- sitive to the full range of context, and lacking in direct relationship to the knowledge base on highway crashes as well as operations. Of specific importance are models used to determine sight distance and to establish controls for horizontal alignment. • Highway design professionals continue to be taught to focus on application of design stan- dards and to believe in the “standards equal safety” mindset. Nuances in performance associ- ated with marginal changes in design dimensions are not part of the normal design process. Knowledge about safety and operational effects is not readily applied as routine practice in design. As a result, much of highway engineering design has become “defensive” in nature, with focus on processes intended to protect agencies from tort liability actions. • Agencies and agency staff remain organized and function in knowledge silos. The role of high- way engineers is to produce a three-dimensional design suitable for bidding and construction. The foundational issues of how the road as designed will operate are too often left to other professionals (traffic engineers, highway safety specialists) whose input may be “after the fact,” or tangential to the tasks the highway engineer. Clearly, the world in which agencies and their staff work has changed considerably since the 1950s. The need for fundamentally different approaches to highway design, viewed from a dis- tance and with the perspective of history, seems self-evident. Following are some items of general concerns and discussions in justification for a need of changes to the current state of practice. • Much of the content of the AASHTO Green Book has either remained unchanged, or not been fundamentally questioned despite both research and anecdotal evidence. Design stan- dards and the basic design models continue to be considered appropriate unless and until proven otherwise. Contents of the AASHTO policy that were products of unproven hypoth- eses in their original formulation remain in place in the policy, unquestioned after many years. Indeed, in some cases lack of documentation and institutional memory is such that the presence of one or more criteria leaves open the question of what its purpose or value is. There

24 a performance-Based highway Geometric Design process remain many criteria that were developed to address the practical issues associated with hand calculations, a need that is long gone. • The direct input of what may be referred to as “external” influences such as environmental effects remains outside the direct application of design criteria to the design process. High- way design processes still rely on a process that labels environmentally sensitive solutions as “design exceptions” rather than as context-appropriate solutions. • The significant variation in context—rural vs. urban, geography, presence of non-motorized road users—is inadequately incorporated in current processes. A significant aspect of context is the basic project type of new vs. reconstructed or rehabilitated roads. These clearly differ. • Process solutions such as VE and CSS, although well intentioned and valuable, have become “add-ons” to the overall design process, adding to both the cost and time to complete an assignment. Moreover, such process solutions, in repeatedly producing challenges to funda- mental design standards or assumptions, raise uncertainty and frustration for highway design professionals who have been taught to follow the design standards. Perhaps most importantly, the size and age of the highway system and the apparent limi- tations in funding its maintenance have yet to be reflected in both the technical and process aspects of highway design. The mindset of a “conservative” designer to upgrade a road to cur- rent standards is no longer the right approach. Indeed, the design standards themselves, which are the building blocks of design, should undergo a thorough review. In the current and future environment, the AASHTO community will ideally recognize the need for the highway design process to be as fully performance-based as possible. Finally, technology and the vastly expanded knowledge base of safety and operations, human factors, and vehicle performance offers opportunities; indeed it demands that the profession make best use of such technology. Highway engineers can be freed-up from the now mundane tasks of alignment calculation and instead focus on incorporating as part of the design pro- cess the many and varied inputs and outputs that may be result from a given set of alternative solutions.