Trade-Off Considerations in Highway Geometric Design (2011)

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49 CHAPTER THREE AGENCY EXPERIENCE formalized process does exist, it is rooted in the conventional design exception process. At the other end of the spectrum, Missouri Department of Transportation (MoDOT) has moved to a philosophy of “Practical Design” in which trade-offs become the everyday way of doing business. To support this approach, MoDOT has developed Practical Design: Meeting Our Customers’ Needs (81). Other agencies such as Colorado Department of Transportation (CDOT) utilize CSS/CSD pro- cedures for evaluating trade-offs and have developed vision- ing documents that outline their approach [Context Sensitive Solutions (CSS) Vision for CDOT (82)]. Similarly, PennDOT has developed tools to aid the consideration of community context for evaluating trade-offs through a detailed form called a Community Context Audit (83). Most agencies evaluate trade-offs during either prelimi- nary engineering or environmental clearance. However, sev- eral respondents sagely point out that trade-offs are often not raised until design is nearly completed. This would greatly reduce flexibility in being able to address the issues associ- ated with the trade-off. One respondent cited organizational difficulties in dealing with trade-offs during the preliminary engineering phase as a result of the agency not having a pre- design unit to handle these types of decisions, with the result that most decisions on design values cannot be undertaken until the design phase. The majority of agencies point to consultant staff as the primary resource for performing the analysis of trade-offs in the design selection process. In addition, the majority of agencies have centralized control of approval authority for the supporting analyses and documentation for these trade-off decisions. Also, most agencies had different units approving the trade-off decisions and approving design exceptions. The role of key staff within the agency was queried: • Chief Engineer. Final approval on design exceptions. • Counsel. Typically not involved in design trade-off decisions. May be asked for legal opinion on tort issues. • Design Project Manager. Responsible for project development, assessment of risk, and documentation of trade-off decisions. • Engineering and Planning Specialists. Develops and evaluates trade-offs and risk. This chapter presents a brief summary of the results of the detailed survey. This discussion is not meant to be all-inclu- sive, but simply to provide an overview of the responses received regarding evaluation of trade-offs in the design selection process, risk, tools and training, agency experi- ence, design exception process, and the future. Each STA has a unique operating environment, and this information is only a general overview of the approaches being utilized across the nation. Appendix A and Appendix B contain the survey instru- ment and detailed responses, respectively. Of the 52 surveys distributed, 43 were returned from the following 41 STAs, as well as the District of Columbia and Puerto Rico: Alabama Kansas Nevada South Dakota Arkansas Kentucky New Hampshire Tennessee California Maine New Jersey Texas Colorado Maryland New Mexico Utah Delaware Massachusetts New York Vermont Florida Michigan North Carolina Virginia Georgia Minnesota North Dakota Washington Hawaii Mississippi Ohio Wyoming Idaho Missouri Oregon Illinois Montana Pennsylvania Iowa Nebraska South Carolina Of the 43 responses, 41 STAs agreed that trade-off con- siderations enter into their process for geometric design decisions. These 41 STAs provided input on the remaining survey questions. Because not all questions were completed by responding STAs, in some instances there are fewer than 41 responses to a particular question. EVALUATION OF TRADE-OFFS IN THE DESIGN SELECTION PROCESS As CSS/CSD becomes more deeply integrated into the high- way design community, more STAs are developing formal- ized processes to take advantage of the tools available to evaluate trade-offs in the design selection process. However, a little more than half of the responding STAs still do not have a formalized process in place, and in many instances where a

50 • Public Information Officer. Typically not involved in design trade-off decisions, but communicates deci- sions once made. During the development of the survey, 11 typical catego- ries of trade-offs were identified for inclusion: access man- agement, cost, environmental issue, historic impact, human factors/driver expectancy, operational efficiency, right-of- way availability, safety, schedule, social concerns, and tort liability exposure. Agencies were asked to represent whether they included the listed trade-offs as project goals in a proj- ect P&N statement (see Table 15). With the exception of tort liability exposure, all other trade-offs were either always or sometimes included in a P&N. Not surprisingly, almost all responding STAs always include safety in the P&N. The other trade-offs that at least half of the agencies always included in a P&N were cost and environmental issues, though opera- tional efficiency falls just below this threshold. The agencies were also asked to identify how goals associ- ated with these typical trade-off categories were measured— quantitatively, qualitatively, or using a combination of both (see Table 15). Cost and schedule were most often measured quanti- tatively. Human factors/driver expectancy and social concerns were most often measured qualitatively. All other categories were measured using a blend of both types of analysis. The agencies were asked to rank the top three categories of trade-offs used as justification for design decisions. Over- whelmingly, the top category was safety. Both cost and envi- ronmental issue showed strongest as the second and third most often used. When all responses were tallied, it was clear that the categories of greatest concern were safety, cost, and environmental issues. Each of these categories received between 24 and 28 total responses (i.e., were selected as either the most often, second most often, or third most often used trade-off). The next most represented trade-offs are operational efficiency at 12 and ROW availability at 10. All other trade-off categories were selected five or fewer times. This clearly demonstrates that most agencies typically focus on a limited number of trade-offs during a design decision. STAs were then asked to rank on a scale of 1 to 10 (10 being very likely) the likelihood of a particular trade-off being accepted as justification for a design decision. Average scores ranged from 5.3 to 8.1 (see Table 16). Continuing the previously identified trend, in the categories of safety, cost, and environmental issue, most respondents ranked the likeli- hood very high (average scores for safety 8.1, cost 7.8, and environmental issues 8.1). The trade-offs of historic impact, operational efficiency, and ROW availability also had high rankings. The rest of the trade-offs’ average scores were near the middle of the range. TABLE 16 AVERAGE SCORES FOR AGENCY RANKING OF TRADE-OFF CATEGORY AS JUSTIFICATION FOR DESIGN EXCEPTION Trade-Off Score Access Management 5.8 Cost 7.8 Environmental Issue 8.1 Historic Impact 7.7 Human Factors/Driver Expectancy 6.5 Operational Efficiency 7.3 Right-of-Way Availability 6.8 Safety 8.1 Schedule 5.7 Social Concerns 5.9 Tort Liability Exposure 5.3 TABLE 15 NUMBER OF AGENCIES RESPONDING REGARDING INCLUSION OF TRADE-OFF CATEGORY AS A P&N GOAL AND MEASUREMENT METHODOLOGY EMPLOYED TO EVALUATE As a P&N Goal Measurement Always Sometimes Never Quantitative Qualitative Both Access Management 6 31 4 8 11 20 Cost 21 18 2 25 2 13 Environmental Issue 21 17 3 2 10 27 Historic Impact 16 22 3 4 14 22 Human Factors/Driver Expectancy 14 21 6 2 19 16 Operational Efficiency 20 21 0 13 5 23 Right-of-Way Availability 16 21 4 14 3 21 Safety 32 7 2 1 5 35 Schedule 12 24 5 20 4 12 Social Concerns 13 26 1 1 25 14 Tort Liability Exposure 9 19 12 2 10 19

51 Next, the agencies were asked to detail the methodology typically used to measure the listed trade-off. The responses have been synthesized to represent the most common received. • Access Management. Expert opinion, engineering judgment, state regulation, or benefit/cost analysis. • Cost. Benefit/cost analysis, cost comparison, expert opinion, or value engineering. • Environmental Issue. Environmental studies, federal/ state regulation, or expert opinion. • Historic Impact. Federal/state regulation, environmen- tal study, or expert opinion. • Human Factor/Driver Expectancy. Expert opinion or engineering judgment. • Operational Efficiency. Traffic analysis/modeling or expert opinion. • Right-of-Way Availability. Benefit/cost analysis, cost comparison, expert opinion, or engineering judgment. • Safety. Expert opinion, engineering judgment, or crash analysis. • Schedule. Expert opinion or scheduling analysis. • Social Concerns. Public/stakeholder input, expert opinion, engineering judgment, and impact matrix. • Tort Liability Exposure. Expert opinion or legal counsel. In almost all instances, STAs document design decisions (other than design exceptions) in some type of project report, file, correspondence, or meeting minutes. The trade-offs associated with these decisions often require examining the acceptable range for a particular criterion. Based on survey responses, the value selected is most often determined by using engineering judgment, expert opinion, benefit/cost analysis, or some type of value assessment. Approximately three-quarters of the STAs responding noted that public involvement plays a role in the approval of a trade-off. However, the comments received regarding how public involvement affected the process were not con- sistent as to what elements of the process can be affected, at what intensity, and how often. For example, one comment stated that public involvement affects the process only if the trade-off under consideration was raised through the pub- lic involvement process, whereas another considered stake- holder input only for items that will not adversely affect safety. Other STAs utilize public input to help make deci- sions and even put stakeholders on the project design team. However, it was stressed that the final decision regarding a design lies with the agency. Most respondents utilize some type of public information meeting as the primary way to communicate these decisions to the public, though some agencies referenced using project websites or press releases. The responding agencies were spilt approximately 50-50 when asked if there were any gaps, problems, or missing com- ponents in the procedures and tools associated with evaluating trade-offs. Those who believed there were gaps were con- cerned that although some guidelines are provided, the evalu- ation of trade-offs usually relies on engineering judgment. Further, evaluation of these trade-offs has become a group decision, which can result in failure to adequately identify exceptions and, thus, may not consider appropriate trade-offs. This is compounded by a lack of experienced staff, sufficient funding, and standardized documentation, as well as inconsis- tencies associated with informal practices at some agencies, and can be influenced by aggressive project schedules and political involvement. Finally, there is a need for more detailed protocols to deal with these trade-offs and their documenta- tion. Those who did not believe that there were gaps pointed to processes and policies that, when followed, minimized gaps. Building on this assessment, STAs identified strengths and weaknesses associated with their current design selec- tion process relative to evaluation of trade-offs. For strengths, the most pervasive responses focused on the inherent flex- ibility in both standards and approach and on establishing complete documentation of decisions. Other comments referred to the use of CSS/CSD to develop an all-inclusive, collaborative design and decision-making process in which the design criteria are based on the context of the project area and interdisciplinary teams are utilized. For weaknesses, many comments echoed those made regarding gaps in the process—inconsistency, lack of experienced staff, lack of staff training, and lack of a clear-cut process or procedure. Other respondents noted that it can be difficult to achieve consensus on trade-offs and that analysis sometimes comes too late in the process. Finally, a concern was raised that the approach does not address a combination of decisions that meet standards, but could still result in poor design. RISK Agencies were asked to define acceptable risk for the use of trade-offs in the design selection process. The following is a sample of the responses: • Acceptable risk would be defined as little to no chance the trade-off would cause an increase in the number or severity of accidents. • Use risk matrixes and evaluate risk on a case-by-case basis. • Most is engineering judgment or based on guidance material. • No such formal procedures are typically used. • There are not tools used to help define acceptable risk. Do not feel comfortable to document an “acceptable risk” on a project. STAs were then asked to define unacceptable risk for the use of trade-offs in the design selection process. The follow- ing is a sample of the responses:

52 • A risk would be considered unacceptable if there is a significant impact to safety considerations. • Reducing safety to deliver a project within the pro- grammed cost is unacceptable. • Unacceptable risk for this agency generally involves reducing safety on a facility (perceived or data driven) or making choices that would delay a project out of a fiscal year or would increase costs to more than 110% of budget. • Risk is only considered informally, so we don’t have a definition. • Expert opinion is used to evaluate risk and determine unacceptable risk on a case-by-case basis by utilizing all available input and data to determine the safety and operational effects of the project. • Risk analysis not undertaken, trade-off determined by the maximum safety and facility benefit with reason- able and available budget. • After completing a design risk analysis and identify- ing strategies to minimize those risks, the residual risk can be compared with the corporate risk tolerance (for example, safety risk). If that level of residual risk can- not be tolerated, additional resources and design strate- gies will be necessary. Approximately three-quarters of the agencies surveyed did not have risk prediction tools or techniques to assist in balancing competing interests in the design process. Those that did cited the use of the HSM, IHSDM, Roadside Safety Analysis Program (RSAP), VE, and crash history as tools for risk prediction. In addition, quantitative risk analysis, risk matrixes, and risk management were identified as tech- niques in use. Of those agencies that cited using risk predic- tion tools or techniques, almost all used ones that contained a mixture of both qualitative and quantitative analysis. TOOLS AND TRAINING Approximately one-half of the responding agencies have specific tools to assist designers in evaluating trade-offs in the design selection process. These tools include the HSM, IHSDM, RSAP, VE, crash history, life-cycle cost analysis, and Design Policy manual. Approximately half also have training to assist designers in evaluating trade-offs, includ- ing classes, workshops, and webinars on geometric design exceptions, context sensitivity, CSS, risk analysis, value analysis, risk management, roadside design, geometric design, and project management. In addition, some agencies cited mentoring as a way of passing on knowledge. AGENCY EXPERIENCE Only five responding agencies have developed specific per- formance goals regarding the evaluation of trade-offs in the design selection process: • Crash reduction goals and right-sizing cost savings goals. • For bridges, rehabilitation work must provide a certain life at an acceptable condition rating to justify the cost of rehabilitation. • Make transportation networks safer, make infrastruc- ture last longer, make organization a place that works well and make organization a great place to work. • Reducing operating expenses and increasing infra- structure investment. • The goals outlined in Target Zero, a strategic highway safety plan. Agencies were also asked to provide examples of success- ful implementation in the design selection process: • The US 285 Environmental Assessment project received an award for CSS. The design implemented some varia- tions to a design based entirely on safety and mobility. This was documented in a paper presented to TRB as part of an NCHRP study currently being conducted. • US 36 – Responded to public input relative to managed lane separation and shoulder design to reduce the proj- ect’s footprint and impacts. • 6th and Wadsworth – Trade-off on superelevation on a loop ramp to reduce ROW impacts. • Parker/225 – Replaced flyovers with left turn lanes. • Downtown Chaska (Trunk Highway 41, still in plan- ning/design): Trade-offs were explored between com- peting cross-sectional width elements to arrive at an efficient and safe cross section and equitable balance. This included design exceptions for lane width and shoulder width. Included in the consideration was the need for a wide raised median for traffic calming and pedestrian refuge. Additionally, nonwarranted traf- fic signals are included in the proposal to aid in safe pedestrian crossings. This was negotiated with the local city, who agreed to make every other cross- street a right-in/right-out condition in exchange for the nonwarranted signals. This project is an example of trade-offs in competing design elements as well as functional, operational, and safety elements. Although nonwarranted signals are typically considered dubious from the standpoint of safety, overall expected safety is improved owing to the pedestrian safety improvement and the leveraged access restriction. • I-235 project had areas of tight ROW in an urban set- ting. There was not enough room in one area to provide required shoulder width without purchasing massive ROW or building complex retaining walls. Interstate standards would have required a 12 ft median side shoulder in this area and there was only room for 6 ft. The shoulders were built at 8 ft. and the lanes were reduced to 11 ft. It was considered safer to have space for a car to get off so the shoulder was built at 8 ft and the lanes were narrowed to 11 ft.

53 • MD5 Leonardtown – Heavy movement of horse and buggy on mainline of state highway. Revised typical section of roadway to accommodate horse and buggy safely with cars. • MoDOT has undertaken an enormous bridge replace- ment program on a greatly reduced budget. Some of the trade-offs involved reasonable roadside hardware con- siderations such as delineation-only option for bridge ends on very low-volume roads. There were hydrau- lic trade-offs such as small increases in upstream rise where appropriate. Deck widths were decreased, employing narrower shoulders on minor road struc- tures. Because of these and numerous other issues, 800 bridges will be replaced or undergo major rehabilita- tion within 3 years at a fraction of the cost of replacing the same number, within the same time span, by con- ventional methods. • On the US 95 widening project in Las Vegas from I-15 to Summerlin, we needed to add additional travel lanes, but the roadway was located in massive cut sec- tion. We couldn’t achieve the shoulder on the median or outside of the travel lanes, so no shoulders were included on the project. This was allowed because it was considered an interim project until the massive project was advertised 5 years down the road. We pro- vided a 24-hr emergency resource van for the 5 years to remove broken down vehicles quickly and to assist on accidents. We continue to have the 24-hr emer- gency resource van because of the positive feedback from the public. • Point Marion Bridge Project, Bridge type selected based on environmental factors. DESIGN EXCEPTION PROCESS STAs were asked to report the number of design exceptions that they typically processed per year. The survey did not ask respondents to specify if these design exceptions were NHS or non-NHS projects. There was a large range in the number of exceptions processed, with a low of 1 and a high of 700 (Figure 35). The average number of exceptions processed was 74. However, this average drops to 41 once the two out- lier data points above 500 are removed. Agencies were also asked to report on the number of design exceptions that were approved in a typical year. Again, there was a large range in the number of exceptions approved, with a low of 1 and a high of 600 (Figure 36). The average number of exceptions processed was 65, but this number drops to 35 with the outliers removed. For a little more than half of the agencies reporting, all design exceptions processed were accepted. For the remain- ing, the number rejected varied between 1 and 148. Thus, on average, between 6 and 10 design exceptions are rejected each year, representing about 15% of those submitted. How- ever, the rate of rejection of design exceptions also varied greatly, between 1% and 80%. Agencies were asked if the advent of CSS/CSD or design flexibility has increased the number of design exceptions they process in a typical year. Approximately three-quar- ters of the agencies that responded reported there had been no change, with a little over 15% reporting that they had increased and 10% reporting that they had decreased. FIGURE 35 Annual number of design exceptions submitted.

54 A previous survey conducted in 2002 as part of NCHRP Synthesis 316: Design Exception Practices (22) also deter- mined the number of design exceptions processed in a typi- cal year. Thirty-one of the agencies that responded to that survey also responded to this survey. As such, it was pos- sible to compare results from the 2002 data with the 2010 data (Figure 37). By and large, the trends exhibited by this data comparison support the agencies’ responses. Agencies commented that the advent of CSS/CSD had not affected the number of design exceptions filed because the use of CSS/CSD does not always translate into design excep- tions. Agencies are generally able to incorporate stakeholder input without having to deviate from accepted guidelines and practices. Other agencies reported that they had been using the principles of CSS/CSD for many years, so there was little impact from simply formalizing the process. However, one agency pointed out that FHWA rarely considers CSS/CSD as an adequate stand-alone justification for a design exception. As such, the principles of CSS/CSD are more frequently used on the state highway network in an informal way. The responding agencies were asked to select the top three types of design exception (based on controlling criteria) for which they typically received requests. Overwhelmingly, the top criterion selected was shoulder width, which scored the highest for the greatest number of requests and overall by a wide margin in both instances. The next highest ranked cri- teria were horizontal alignment, vertical alignment, and lane width, which received less than half the number of responses of shoulder width. Notably, structural capacity received no responses, and additional comments provided in the survey margins stated that this criterion would never be considered. STAs were then asked to rank on a scale of 1 to 10 (10 being very likely) how willing they typically are to con- sider a design exception for a particular controlling crite- ria. Average scores ranged from 2.0 to 7.7 (see Table 17). As determined previously, the criterion that received the great- est number of requests for design exceptions was shoulder width, which also had the highest likelihood of acceptance at 7.7. Of the other highly ranked criteria, horizontal align- ment (average 5.7), vertical alignment (average 6.4), and FIGURE 36 Annual number of design exceptions accepted. FIGURE 37 Change in design exceptions processed (2002 vs. 2010).

55 lane width (average 6.2) also had high likelihood of design exception acceptance. In addition to these criteria, grade (average 6.1) was also highly ranked for likelihood of design exception acceptance. Structural capacity (average 2.0) was poorly ranked, confirming the comments regarding its acceptability. TABLE 17 AVERAGE SCORES FOR AGENCY RANKING OF WILLINGNESS TO CONSIDER DESIGN EXCEPTION FOR 13 CONTROLLING CRITERIA Design Exception Score Design Speed 3.9 Lane Width 6.2 Shoulder Width 7.7 Bridge Width 5.5 Structural Capacity 2.0 Horizontal Alignment 5.7 Vertical Alignment 6.4 Grade 6.1 Stopping Sight Distance 4.5 Cross Slope 5.4 Superelevation 5.5 Vertical Clearance 4.5 Horizontal Clearance 5.2 Almost all of the responding agencies stated that their cri- teria for new construction were the same as the AASHTO Green Book. However, for the controlling criterion of verti- cal clearance, approximately one-quarter of the respond- ing agencies stated that the STA’s criteria were greater than AASHTO’s. Agencies were then asked to relate the most common trade-offs associated with each of the controlling criteria. Those most represented are listed in order of prevalence: • Design Speed – Cost, Safety, and Right-of-Way Availability. • Lane Width – Right-of-Way Availability and Cost. • Shoulder Width – Right-of-Way Availability, Cost, Environmental Issues, and Safety. • Bridge Width – Cost, Safety, and Environmental Issue. • Structural Capacity – Cost and Safety. • Horizontal Alignment – Right-of-Way Availability, Safety, and Cost. • Vertical Alignment – Cost, Safety, and Right-of-Way Availability. • Grade – Cost, Safety, and Right-of-Way Availability. • Stopping Sight Distance – Safety, Cost, and Right-of- Way Availability. • Cross Slope – Safety and Cost. • Superelevation – Safety and Cost. • Vertical Clearance – Cost, Safety, and Operational Efficiency. • Horizontal Clearance – Cost, Safety, and Right-of- Way Availability. Next, agencies were asked to list the most common miti- gation measures utilized for design exceptions of the cor- responding controlling criteria: • Design Speed – Signage and reduce posted speed limit. • Lane Width – Signage and reduce posted speed limit. • Shoulder Width – Signage, various roadside treatments (e.g., guardrail, increased clear recovery zone) and rumble strips. • Bridge Width – Signage, delineators and none. • Structural Capacity – Not applicable or not consid- ered, posted weight limit and signage. • Horizontal Alignment – Signage and reduce posted speed limit. • Vertical Alignment – Signage and reduce posted speed limit. • Grade – Signage. • Stopping Sight Distance – Signage and reduce posted speed limit. • Cross Slope – Signage and none. • Superelevation – Signage, reduce posted speed limit and improve drainage. • Vertical Clearance – Signage. • Horizontal Clearance – Signage, guardrail, delinea- tion and none. FUTURE Agencies were asked if there were any plans to reevaluate how they evaluate trade-offs in the design selection process in the next 6 to 12 months. Approximately three-quarters of the responding agencies stated that there were none. These agen- cies stated in some form that there was an adequate process in place that worked well. The comments from the one-quarter that will be considering potential changes focused on periodic reviews of all processes and updates resulting from regular reevaluation of the project development process. In addition, one agency is developing policies and recommendations for the implementation of a practical design concept. Further, agen- cies referenced the need to update policies and procedures for evaluating trade-offs to account for the new HSM techniques. Agencies were then asked if there were any plans to reevaluate how the agency evaluates design exceptions in the next 6 to 12 months. Only a little over 10% of the responding agencies have plans to update these procedures. They cited a need to place more emphasis on risk and cost related to design exceptions and to incorporate training on mitigation strategies. However, most agencies responded that they had an adequate process in place.