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Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions. 1 Summary 4 Chapter 1 Introduction 4 1.1 Background and Motivation 5 1.2 Study Approach and Synthesis Organization 6 Chapter 2 Review of the Literature 6 2.1 Introduction and Approach to the Literature 7 2.2 Defining and Understanding the Value of Low-Volume Roads 10 2.3 Prioritization Practice 19 2.4 Review of the LiteratureâKey Observations 21 Chapter 3 Survey of Agency Practice 21 3.1 Overview 21 3.2 Survey Instrument, Distribution, and Response 23 3.3 Survey Results: Experience with Prioritization of Low-Volume Roads 33 3.4 Survey of PracticeâKey Observations 35 Chapter 4 Case Examples 35 4.1 Overview 36 4.2 Individual Case Examples 48 4.3 Case ExamplesâKey Observations 50 Chapter 5 Conclusions 50 5.1 Motivation for Granting Low-Volume Roads Special Consideration 51 5.2 Approaches to Defining and Differentiating Low-Volume Roads 51 5.3 Methods for Prioritizing Low-Volume Road Investments 52 5.4 Evolving Issues in Low-Volume Road Planning and Management 52 5.5 Successes and Challenges in Current Practice 53 5.6 Knowledge Gaps and Suggestions for Future Research 55 References 59 Appendix A Survey Questionnaire 68 Appendix B Survey Respondents C O N T E N T S
1 Low-volume roads (LVRs) are at a disadvantage relative to other roads within traditional investment prioritization processes that focus on volume-based metrics of benefit and impact. However, LVRs can also create significant value for the wider economy and society, by providing basic access to remote communities, ensuring connectivity (particularly last- mile connectivity) for industry to a global economy, and supporting economic development opportunities. A growing recognition of the need to go beyond standard transportation asset management approaches to capture the importance of LVR investments in agency prioritization practice motivated this research. The report documents current practices used by transportation agencies to make invest- ment decisions about LVRs. The intention of the report is to help transportation officials in charge of resource allocation decisions at state departments of transportation (DOTs), as well as at regional and local agencies, respond to the challenge of accounting for broader economic, social, and environmental implications of LVR projects. The report also addresses the challenge that decision makers may face to communicate the value of such investments to stakeholders in an era of limited funds and constantly changing demands on the transpor- tation system. The primary focus of the synthesis is on investment prioritization methods. However, the research also touches on a range of decision-making issues including funding program definition, programmatic resource allocation, and other planning and management activities that directly affect investments made in LVRs. The principal intended audience of the research is practitioners within state DOTs. The objective of ensuring adequate investment in LVRs is particularly relevant to state DOTs because of the range of roadways they own, manage, and prioritize relative to one another on an ongoing basis. Municipalities and counties tend to have lower volume roads on their systems, in general, and therefore may not face the same challenges as states with priori- tization imbalances created by volume-based criteria. Nevertheless, this research can also offer value to engineers and planners within local governments and counties where there is interest in accounting for economic, social, and environmental impacts of LVR investments. The report discusses and presents the following: (a) review of North American and inter- national planning and prioritization literature for LVRs, including consideration of their definition, importance, and available evaluation methods; (b) results from a survey of state DOTs and Canadian provincial transportation agencies regarding their current approaches to LVR investment prioritization (40 out of 50 state DOTs completed the survey for a response rate of 80% and three provinces also responded); and (c) six detailed case examples of the current state of the practice for prioritization of LVRs with a focus on how critical strategic issues, that is, the broader social, economic, and environmental importance of LVRs, are considered within an agencyâs process. S U M M A R Y Investment Prioritization Methods for Low-Volume Roads
2 Investment Prioritization Methods for Low-Volume Roads The literature review, survey responses, and case examples all point to common agree- ment that LVRs can be important in ways that go beyond the level of traffic they carry, and that their significance merits special consideration within the planning and resource alloca- tion process. Exactly how that special consideration is implemented varies across agencies, in part because of differing definitional approaches to LVRs, as well as to programs of work within the resource allocation process. A significant number of state DOTs do actually define LVRs as a distinct class, based on volume thresholds and/or alternate approaches that relate to an agencyâs overall road classification scheme. Even those agencies that do not adopt formal LVR definitions nevertheless describe the practice of dividing their networks into different classes that often correlate with volume to guide agency decision making. States additionally vary in the scope of the low mileage network for which they are respon- sible, with some states managing much larger overall systems than other states. Nearly all LVR investments in the United States are related to safety or state of good repair rather than to system expansion. Nevertheless, agencies clearly see value in maintaining existing LVRs because of their role in providing access to rural or isolated areas and support- ing economic activity (e.g., farming, logging, mining, or other industry), as well as for their network coverage role within the broader transportation system. When making decisions about how to prioritize LVR investments (whether against each other or against other invest- ments on higher volume facilities), decision makers typically begin with core quantitative data including asset condition and transportation-related conditions or impacts (e.g., travel time or accident rates). At state transportation departments in the United States, these data are often organized and analyzed within pavement and bridge management systems. Recog- nizing that more traditional engineering analysis cannot capture all key decision variables, most transportation agencies then supplement with a mix of quantitative ratings, qualita- tive scoring (e.g., 0 to 10), and descriptive approaches to capture the economic, social, and environmental conditions or impacts of LVR investment decisions. The literature review also finds that there can be insights derived from both domestic and international experiences, including the body of research and practice from countries all along the development spectrum. While there are notable differences among countriesâ including the level of roadway infrastructure already in place and the available systems, data, expertise, and institutional capacity for managing that infrastructureâthere are never- theless key commonalities, particularly with respect to the economic development and basic access objectives of LVRs. The literature review provides examples of how to incorporate these common objectives into decision making in a way that extends beyond traditional engineering and asset management criteria. The literature review additionally includes documentation of different prioritization methods used globally including consumer and producer surplus based methods, processes for screening alternatives, benefitâcost/costâ benefit analysis, cost-effectiveness analysis, and multicriteria analysis. Focusing on state DOT practices, the individual case examples reveal the close relation- ship between statesâ desire to recognize the broader strategic importance of LVRs in serving communities and their reliance on local knowledge. In particular, because of their familiarity and close relationships to the communities they serve, district or field engineers help ensure that the prioritization process recognizes the broader (and often harder-to-quantify) role of LVRs. This recognition is achieved through processes with varying degrees of formality, ranging from open qualitative input to more structured use of qualitative scoring criteria. Quantitative measures of strategic importance are less common, although certain indicators such as measure of economic distress, poverty, or accessibility do appear in the literature as a way of raising one roadway or candidate project above another project. Funding limitations strongly influence the LVR prioritization conversation. Agency survey responses report a mix of perceptions of trends in LVR importance. On the one hand, some
Summary 3 agencies report decreased attention paid as funding constraints push agencies to direct their resources elsewhere. On the other hand, the same funding pressures are causing others to take a closer look at LVRs and their role within the broader transportation system. Going forward, LVRs may emerge as âfrontlinesâ in efforts to ârightsizeâ transportation system investments. When states grapple with the challenges of matching system size and invest- ment levels to societal needs, the ability to distinguish between different facilities with varying degrees of importance is likely to become even more critical. Also of note are the inter dependencies reported by transportation planners between federal policies and a state DOTâs decisions about LVRs; whereas performance management and target setting are focused in accordance with federal policy on the National Highway System, LVRs are typically not on this system, and therefore may receive a different level of attention. Most state DOTs report satisfaction with their current approaches to prioritizing LVR investments. In particular, the synthesis documents success experienced by states when implementing prioritization approaches that are flexible and able to incorporate local judg- ment and knowledge. Nevertheless, there were remaining knowledge gaps identified in the course of the synthesis that further research could address. The following are suggested topics that would benefit states and localities charged with managing and prioritizing LVRs: â¢ Structured best practices approaches to incorporate broader strategic objectives of LVR investments into decision making; â¢ Methods for jurisdictional transfer evaluation to support the goal of rightsizing highway networks; â¢ Guidance on interjurisdictional partnering and coordination in funding and prioritization of local LVR improvements; â¢ Approaches to optimizing tiered level of service targets as a function of agency and societal costs; and â¢ Understanding threshold effects from long-term reductions in LVR performance. The conclusions chapter discusses these research topics in more detail. Finally, it is worth noting that broader efforts to incorporate strategic objectives into resource allocation deci- sion processes in general may ultimately result in useful advancement in LVR prioritization practice.
4 1.1 Background and Motivation The purpose of this synthesis is to document current practices used by transportation agencies to make investment decisions about low-volume roads (LVRs). This synthesis adopts a flexible approach to classifying LVRs, recognizing that definitions are context dependent and that LVRs can be defined both in strict volume terms, and on the basis of other criteria that agencies use to segment their networks by relative importance or by similar usage patterns and needs. This research responds to interest in methods that address the economic, social, and environmental impacts of LVR investments. While current investment practices make use of asset condition, traffic, and safety metrics, these types of metrics may not always be sufficient to direct scarce resources toward roads and projects that will result in the largest overall gain in societal well- being and performance. Put simply, volume is not the whole story. Recognizing that LVRs may not be able to compete with other facilities using traditional engineering measures of impact, the research investigates holistic approaches to factoring road purpose or function into prioritization methods, by documenting and collecting insights from the current state of the practice. The synthesis responds to and builds on several strands of recent and ongoing research. International experience, including studies in the developing world, offers important thinking on the broader societal and economic roles played by low-volume facilities, as well as a global perspective on common challenges associated with the management of these roads. This research also dovetails with increased emphasis in recent years on bringing economic, social, and envi- ronmental considerations into investment evaluation methods. Existing practice has tended to focus more on large capacity projects because of the scale of their impacts. Attention, however, is redirected toward understanding the strategic importance of smaller roads and projects even in cases where the user base is relatively limited or the impact is incremental. This in turn relates to ongoing and increasingly urgent interest in the value of maintaining infrastructure in a state of good repair. Just as it is a challenge to measure and communicate the impact of LVR projects because of their scale, it is similarly a challenge to measure and communicate the impact of maintenance and preservation activities, in comparison to the impact of larger expansions proj- ects. This challenge is not unique to LVRs, but it is particularly salient for LVRs because LVR investments tend to be for preservation and maintenance. The issue of LVR investment and maintenance also directly relates to national conversations about limited funding and trade-offs between expansion and preservation, in that LVRs can carry relatively small proportions of total travel served but comprise relatively large proportions of system mileage and agency preservation responsibilities. Given this background, the synthesis endeavors to serve agencies interested in holistic approaches to LVR prioritization, including recognition of factors beyond the traditional volume, conditions, or safety metrics that might serve to elevate an LVR in the list of investment priorities. C H A P T E R 1 Introduction
Introduction 5 1.2 Study Approach and Synthesis Organization Responding to this background and research motivation, this synthesis addresses how different transportation agencies are responding to the need to prioritize potential investments in LVRs. This synthesis regarding methods used by agencies for prioritizing LVR investment draws on information from three sources. They are (1) a literature review of published studies about investment strategies for LVRs, with both domestic and international sources represented; (2) an online survey of state DOTs and Canadian provincial transportation agencies; and (3) in-depth interviews with decision makers responsible for LVRs at state agencies. The study documents the different ways that agencies define LVRs, the ways in which they may treat these roads differently from other roads within their planning and investment processes, and the approaches used for addressing strategic issues related to LVRs including economic, social, and environmental impacts. The following chapters of the report address these issues: â¢ Chapter 2 summarizes current knowledge, practices, and relevant research pertaining to investment prioritization methods for LVRs, as documented in published research and agency reports. While acknowledging the array of engineering and design-related literature available for LVRs, the review focuses specifically on literature-related planning and investment priori- tization issues, both domestic and abroad. â¢ Chapter 3 reports on the current state of the practice for LVR prioritization, based on find- ings from the survey of practitioners. Data are compiled for the 40 out of 50 state DOTs that responded (80% response), along with three Canadian provinces. â¢ Chapter 4 provides six in-depth profiles of state DOT practice with respect to LVR planning and investment strategies. The case examples address LVR definition, address the treatment of these roads within the investment process, address consideration by agencies of critical strategic issues related to LVRs, and provide a snapshot of trends and interest in practice improvement from the perspective of interviewed practitioners. â¢ Chapter 5 synthesizes the major findings of this research and provides overall lessons learned about the state of the practice as well as suggestions for future research. â¢ Appendix A contains a copy of the full questionnaire and Appendix B is a list of agencies that responded to the survey.
6 2.1 Introduction and Approach to the Literature This chapter summarizes current knowledge, practices, and relevant research pertaining to investment prioritization methods for LVRs. While there is broad agreement on the value of approaching LVRs differently from other roads, the definition and understanding of LVRsâ significance vary throughout the literature. This chapter is organized to answer a series of questions to help situate LVRs within a broader decision-making process before examining specific methods used to evaluate LVR investments. These guiding questions include â¢ Definition and significance. What is a low-volume road? What attributes of LVRs can make them more significant than volume-based metrics alone would suggest? â¢ Low-volume road in the planning process. Where does an LVR typically appear in the planning and investment process? What types of decisions are most relevant to LVRs and who is responsible for making these decisions? â¢ Low-volume road and prioritization. What types of practices and methods appear in the liter- ature for evaluating LVR investments? How are broader social, economic, and environmental considerations addressed? What documented challenges constrain the ability of practitioners to address the full importance of LVRs in their management and prioritization strategies? The relevant research was assembled from three primary sources: (1) TRBâs Transportation Research Information Database, which includes records of both national and international research; (2) papers and proceedings from the international conferences on LVRs organized every 4 years by the Transportation Research Boardâs Standing Committee on Low-Volume Roads; and (3) references suggested by members of the project panel. The research was supple- mented by targeted web searches and in select cases with documentation provided by state DOT questionnaire respondents. More details on the questionnaire survey are in Chapter 3. Chapter 4 contains in-depth consideration of specific state practices. The body of available literature on LVRs encompasses both engineering and planning-related materials; experience from North America, other Organisation for Economic Co-Operation and Development countries, and the developing world; and a mix of theoretical (academic) research, documentation of applied methodologies, and published guidelines related to the management of LVRs. While all of these types of literature exist, the balance of published research is more strongly concentrated in engineering and design, with planning and prioritization considerations addressed in a smaller subset of the literature, or tangentially within more engineering-oriented literature. In addition, there is a particularly strong line of research relating to LVRs in inter- national development. The resources cited in the remainder of this chapter were intentionally culled to focus on planning and prioritization issues and to learn from a broad range of practice across the globe, while maintaining a focus on situations that are analogous to those faced by state DOTs and other practitioners in North America. C H A P T E R 2 Review of the Literature
Review of the Literature 7 2.2 Defining and Understanding the Value of Low-Volume Roads 2.2.1 Definitions of Low-Volume Roads Volume-based definitions. There is no single approach to defining LVRs. There are varying volume thresholds published, particularly for the purposes of setting design guidelines. In the United States, the American Association of State Highway and Transportation Officials devel- oped geometric design guidelines for âvery low-volume local roadsâ with average daily traffic (ADT) of 400 or less (AASHTO 2001). Other transportation agencies have adopted this thresh- old. Examples include South Dakota DOTâs sponsored research on local road surfacing criteria (Zimmerman and Wolters 2004); the U.S. Agency for International Developmentâs Low-Volume Roads Engineering: Best Management Practices Field Guide (Keller and Sherar 2003); the Delaware Manual on Uniform Traffic Control Devices (MUTCD) (Delaware DOT 2012); and Indianaâs design guidelines for historic bridges on LVRs (Uremovich 2007). Some states have adopted definitions of LVRs in order to define the scope of special funding programs. Pennsylvania legislatively defined LVRs through Act 89 of 2013 with a funding set- aside that applied to roads âsealed or paved with an average daily traffic count of 500 vehicles or lessâ (Pennsylvania State Conservation Commission 2014). Similarly, Oregonâs Low Volume Preservation Program applies to ânon-Interstate highways with average daily traffic of less than 5,000 vehicles and 20-year equivalent single-axle truck loads less than three millionâ (Coplantz 2014). Oregonâs definitional threshold has in fact changed over time since the programâs inception in 1999, as the agency has refined its approach to investment strategies. Faiz pointed out that the Federal Highway Administration aggregates âall rural arterials with an AADT [Annual Average Daily Traffic] of 1,000 or less in a single categoryâ within published U.S. Highway Statistics (2012). Faiz explained this threshold as having broad global appeal because it is a threshold at which âhigher design speeds and related standards (wider lanes, paved shoulders, gentler curvature) kick in,â although others have set the bar as high as 2,000 or even 5,000 AADT (Faiz 2012). Within the international literature, there are also guidelines and papers that set volume thresholds for various design and evaluation practices. Examples include Archondo-Callaoâs development of an economic decision model specifically for unpaved roads with traffic less than 200 vehicles per day in Africa (1999), or similar research by Benmaamar, who developed an appraisal method that would be appropriate for facilities below 200 AADT in Tanzania, where typical approaches may not be suitable (2003). Guidelines developed for low-volume sealed roads in Southern Africa also adopt a 200-vehicles-per-day threshold (Pinard et al. 2003). Moya et al. suggested four volume classes under 450 ADT for management of Spainâs LVRs (2011) and Edvardsson focused on roads carrying up to 1,000 vehicles per day in her investigation of Nordic literature on LVRs (2013). Beyond volume. Looking beyond volume, some literature opts to focus instead (or, in some cases, also focus) on a facilityâs location (rural versus urban), ownership, functional classifica- tion, or some combination thereof. Agarwal et al.âs LVR research in India specifically addressed maintenance and prioritization challenges for rural facilities (2016). The explicit or implicit conflation of rural roads and LVRs is common. Kemp et al. in Australia (2016) and Chicoine et al. in the United States (1989) focused on rural facilities, with further stratification by owner- ship. From an engineering perspective, Douglas explained how a countryâs road classification system is typically the starting point for design decisions (2016). More broadly, classification and ownership provide a frame for practitionersâ understanding of LVRs. For example, the federally defined High Risk Rural Roads Program focuses on rural major and minor collectors and rural