A Performance-Based Highway Geometric Design Process (2016)

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D-1 This appendix identifies the typical decisions that could be made during the highway geomet- ric design process and make significant impacts on O&M cost and the life-cycle efficiency of the roadway infrastructure. Examples of the typical design options for consideration during the design process are also highlighted and the liabilities associated with the designer’s options are discussed. A conceptual framework for incorporating O&M considerations into the geometric design process is described with suggestions for future research. This framework is intended for use and develop- ment by designers to suit their specific project or program needs. Introduction O&M often carries a number of definitions. Within this appendix the following definitions apply: • Operations—operations activities respond to the facility objectives, including providing mobility, travel time reliability, safety and security for the road users, and the onsite maintenance/ construction crew. Examples of activities include traffic incident management and work zone management. For the purposes of this section, geometric design refers to all the aspects of the operations of highway activities including determining the length of work zones per each phase of construction. • Maintenance—routine and periodic maintenance activities including pavement resurfacing that are conducted to allow for the safe and efficient operation and use of the highway. Examples of routine maintenance activities include debris removal, mowing, snow removal, pavement patching or crack repair, and drainage clearing. Examples of periodic maintenance include replacement of pavement joints, overlay, or guardrail replacement. Whether designing new highways or implementing improvements or other changes to existing highways, it is important to consider the impact of design decisions on the ease, frequency, and cost of future mainte- nance that the design will have. A project that is hard to maintain may become unattractive and cease to serve its intended operational purpose due to maintenance difficulties. The geometric designer’s objective should be to provide a design that is fit for purpose, while keeping the future maintenance liability to a minimum. Consideration of Operations and Maintenance during Geometric Design Currently, in a typical project development effort, only the capital costs of a project are con- sidered as part of the project development. In a few cases, the feasibility of future maintenance may be considered, but the cost of future maintenance is typically not. The concept of closing a A p p e n d i x d Operations and Maintenance Considerations for Geometric Design

D-2 A performance-Based Highway Geometric design process lane/s for incident management, street sweeping, tree trimming, or maintenance of the ditch are not among the typical design decisions considered by the designers. It is important to consider future maintenance costs and activities during the planning/design stage of any significant infrastructure investment, including a highway project, as decisions made early in the life cycle can have a material impact on future maintenance costs. In addition, the safety performance of the operations should be better understood and informed decisions should be made in implementing the improvement. Therefore, consideration during the design process of how a highway is to be maintained is beneficial to the owner with future responsibility for maintenance costs and provides assurance that the system can be maintained as designed. Finally, failure to adequately consider O&M during design may increase the risk of future liability. As noted previously, maintenance functions are ministerial in nature and subject to tort claims if not carried out properly or within a reasonable time. Consider, for example, the geometric design of a curve that drains poorly, and which has guardrail along the edge of shoulder. If run-off-road crashes occur with great frequency involving vehicles striking the guardrail, the owning agency will suffer great pressures (in addition to high costs) to continually repair and replace the guardrail. Failure to do so in a timely manner may produce tort liability risk if a driver strikes a section of guardrail that is unrepaired and hence not functioning as intended. If O&M is not considered at each stage of the design process there is the potential that additional mitigation measures will be required during later stages of the project life cycle, often at disproportionate additional cost, or that the design may need to be reworked. The following summarizes the key reasons for the incorporation of O&M considerations in the geometric design process (Roads in Hertfordshire: Highway Design Guide, 3rd Edition, Section 2: Highway Layout and Strategies, Chapter 7: Design for Maintenance): • Effectiveness—A project that is inexpensive and simple to maintain is much more likely to be maintained, meaning that the project will stay in good condition for much longer and continue to fulfill its purpose. • Cost—There are limited resources for construction and maintenance. Future maintenance liabilities can be eliminated or reduced through careful and effective design. To minimize costs, consideration should be given to whole life-cycle costs, including design, construction, and O&M. • Disruption—Frequent maintenance is disruptive to communities and road users. Assets that are easy to maintain will help to minimize disruptions. This translates into better service provision. Designing with maintenance in mind leads to an asset that needs less work to remain in good operating condition. • Responsibility—At a limited number of locations, facilities on the same right-of-way and/or structures are operated and maintained by different entities. Example: a county road over a freeway in which the county owns the roadway but the bridge belongs to the state DOT; also the signal operation at the ramp terminal intersections with the county road. In this case, the overall design must consider access issues for both parties as well as facilitate agreed to O&M protocols. • Environment—Maintenance work has an associated carbon footprint, whether resulting from the vehicles and equipment used to cut grass or clean drains, or from the energy and raw materials used in producing, transporting and laying asphalt. Reducing the need and frequency of future maintenance will help to reduce the impact on the environment. An important consideration that geometric designers should consider is ease of maintenance or access. If difficult, there will be greater traffic management costs and greater potential risk to maintenance workers. The designer needs to consider how the need for maintenance can be

Operations and Maintenance Considerations for Geometric design D-3 either avoided or minimized and, where it is required, how maintenance can be made easier and safer. This is best done by involving experienced maintenance staff throughout the geometric design process, and especially early in the process when right-of-way and alignment and cross- section dimensions are being set. When Should O&M Be Considered during the Geometric Design Process? O&M should be considered at the time of developing project alternatives, including funda- mental issues surrounding route choice and purpose. Organizations responsible for future main- tenance should be consulted at the earliest opportunity and then at regular intervals throughout the design/planning process. Improvements to the safety and efficiency of maintenance operations can be introduced at any stage of the design process, but with varying degrees of potential impact and cost. The greatest scope for providing improvements in safety is during project preparation; particularly on projects where additional right-of-way is required. Depending on the type of project improvement, stakeholder workshop sessions could be initi- ated at the start of the project development process (and continued throughout as necessary) as they will allow significant or unusual hazards to be identified and either eliminated or any remaining residual hazards to be mitigated, at minimum cost and disruption to the design. Carrying out design reviews at key stages of the design process is an appropriate means of ensuring that prog- ress is made in the management of risk, and that any strategy is monitored throughout the design phase. Typical projects developed under CSS policies require that the stakeholders be engaged in the design development. Regardless of project type and context, every project requires the designer to assess and manage trade-offs among important variables of interest to stakeholders and the owning agency. Risks can be identified and communicated to others at every stage of the process. The Design Manual issued by the Washington State Department of Transportation (WSDOT) dedicates a major section (Chapter 301) to discussing the best practices to improve coordina- tion between designers and maintenance personnel during the project design stage. One of the suggestions is to develop tangible maintenance performance measures to help designers evaluate design alternatives. The WSDOT Design Manual also emphasizes the importance of considering the full life-cycle cost for maintaining certain roadway features. A life-cycle cost analysis (LCCA) to quantify the maintenance and operation cost of design alternatives is a very powerful tool to help designers justify the final asset decision. The WSDOT Design Manual provides an example of a Design Option Worksheet, used to show how a life-cycle cost assessment can be used to determine the optimum solution to address a design for maintenance issue (Exhibit 301-2 Design Option Worksheet Showing Example of Life-Cycle Cost Assessment, example page 136). Although this is for the redesign of a section causing maintenance access problems, it shows (a) the issues caused through failure to consider maintenance needs during design and (b) an approach to use in assess- ing the design alternatives. Can O&M Considerations Be Incorporated within the Geometric Design Process The consideration of O&M can been seen as a discrete overlay that can sit atop of other design decisions, and each decision can be evaluated through the use of LCCA models and cost-benefit analysis (CBA) approaches that are common within the industry. It can be summarized in the

D-4 A performance-Based Highway Geometric design process form of a Maintenance and Repair Strategy Statement,11 or similar, and in this way design decisions can be documented for future reference and for reconsideration in the future as required. When designing the geometry of new highways, it is important for designers to consider the impact that the design will have on future maintenance and operation requirements. Communication between designer and maintenance engineer throughout the design process is crucial, such that the geometric design can be adjusted to improve road safety and to minimize the future maintenance frequency and cost. There may be challenges in the coordination process, as proposed designs may need new/different O&M practices. Tool Development Although maintainability is part of the evaluation process during highway design, the focus of the design process is always toward the construction aspects. Whole LCCA, which includes both construction cost and maintenance/rehabilitation cost is often neglected or addressed qualita- tively. To understand different design parameters and their impact on the future maintenance cost, it is essential to develop a quantitative model of the average maintenance costs of specific geometric designs. O&M considerations for highway design are frequently mentioned in DOT design manuals (see, for example, the Connecticut, Texas, and Virginia DOT design manuals). However, the O&M advice provided in manuals is typically qualitative. Designers need quantitative information on the impacts of their decisions. The FHWA LCCA tool provides an interactive way to do this for pavement design applications and serves an example of the type of model that is needed for O&M cost applications. FHWA LCCA software12 allows designers to perform LCCA for pavement selection in accor- dance with FHWA design methods. The LCCA model requires many project-level input parameters such as hourly traffic distribution, vehicle stopping costs, road user cost, maintenance work zone assumptions, etc. The model is also able to perform risk analysis based on user-defined probability functions. (Figure D-1) Developing a maintenance cost model, similar to the FHWA LCCA model, will help design- ers and maintenance personnel to understand the incremental maintenance costs of different geometric design alternatives. In particular, the model should address the geometry of roadway elements such as shoulder width, maintenance access, roadside slope, etc. It is suggested that the life-cycle model inputs could be divided into three categories, project-level inputs, geometric design, and cost inputs. These categories are described in the following sections and tables (Tables D-1 through D-3): Project-Level Inputs: Project-level inputs are pieces of information that apply to all geometric design alternatives. 11CIRIA Report C686 Safe Access for Maintenance and Repair. Guidance for Designers, 2nd edition 2009. http://apps.trb.org/ cmsfeed/TRBNetProjectDisplay.asp?ProjectID=373. 12FHWA LCCA model—https://www.fhwa.dot.gov/infrastructure/asstmgmt/lccasoft.cfm. Interim Advice Note 69/15, Designing For Maintenance (April 2015), Roads in Hertfordshire: Highway Design Guide. 3rd Edition, Section 2: Highway Layout and Strategies, Chapter 7: Design for Maintenance. Maintenance Considerations in Highway Design, Road Engineering Journal, Copyright © 1997 by TranSafety, Inc. National Highway Research Program (NCHRP) Project 14-9 (2) and NCHRP Report 349 “Maintenance Considerations in Highway Design.” The Institute of Asset Management, Asset Management—An Anatomy, Version 2, July 2014, www.theiam.org Washington State Department of Transportation, Design Manual M 22-01.11, July 2014.

Operations and Maintenance Considerations for Geometric design D-5 Figure D-1. Example of LCCA model from FHWA— RealCost 2.1 Switchboard. setoN tupnI ecnanetniam enituor rof stniop ssecca fo rebmun/eziS sseccA Vertical alignment Key design parameters descriptions including items such as maximum grade Horizontal alignment Key design parameters descriptions including items such as minimum curve radius Cross slope sretemarap ngised dna noitpircsed ngised eganiarD eganiarD Intersection Type of intersection, such as stop, signalized, and roundabout enal ciffart fo htdiw dna rebmuN enaL Lateral offset Width htdiW naideM Right-of-way Area htdiW redluohS Roadside Slope Gradient Table D-2. Geometric design inputs. setoN tupnI Project details To identify the design alternative. It is not going to affect the analysis results Analysis period Number of years that the design alternatives will be compared Discount rate To calculate present value raey ngised fo ciffart yliad egareva launnA TDAA Traffic growth rate The percentage growth rate of AADT Rural or urban traffic User cost is higher in urban roadway sepyt elcihev tnereffid rof emit resu fo eulaV tsoc resU l accident ataf ro suoires ,ronim sa hcus setamitse tsoc hsarC tsoc hsarC Table D-1. Project-level inputs.

D-6 A performance-Based Highway Geometric design process Geometric Design Inputs: This part of the model requires the input of different design alternatives. Users can select up to a certain number of roadway elements to compare their life- cycle cost. Results and Reports: Based on the above three category inputs, analyses could be conducted to meet the objectives of the project development and provide the decision makers comprehen- sive life-cycle costs based on considerations beyond the typical capital construction costs alone. Some default reports could be developed to compare the results of different alternatives. With further development, the maintenance model can be a powerful tool to optimize the life-cycle cost of a highway design. Geometric Design Options The design profession needs a robust and complete knowledge base and toolkit that relates geometric design elements and decisions to the full range of O&M activities. Such a toolkit is beyond the scope of this project; but to advance the thinking in this field the following qualitative guidance is offered. Table D-4 provides a list of sample potential design options with consideration to the individual design elements. This table was assembled by the research team, supplemented by experts in road maintenance and operation. Initial and general ratings are provided for the estimated impacts on the geometric options in four basic areas: • Capital costs—costs of initial construction. • Life-cycle efficiency—efficiency of O&M after construction over the life cycle of the asset. • Maintenance safety—safety of maintenance workers. • Owner liability—risk to owner including claims, reputation, and other costs, direct and indirect outside of O&M. Several examples of the potential geometric design decisions and the rating of the associated category are provided in three basic categories: 1. Horizontal/Vertical alignment. 2. Cross-Section elements. 3. Roadside design. These are the categories of items that were identified to have a predominant effect on the life-cycle maintenance activities and the items/potential pitfalls of the typical geometric design. These examples/categories can be further developed to make a comprehensive list at a detailed level to address the overall project’s O&M, or could be developed for individual project type such as 3R, New Construction, and Reconstruction categories, in addition to the category of the facility types. In addition to the standard design criteria, these O&M related design options could be used in the design development process. setoN tupnI Construction cost Total construction cost of the project Maintenance frequency Different design alternative might require maintenance frequency. For example, pavement built at mountainous terrain requires more frequent maintenance than pavement at level terrain Maintenance cost Total maintenance cost in base year Work zone hours Total work zone hours for the maintenance operations Crash societal costs Developed from the predicted crash frequency methodologies Table D-3. Cost inputs.

Operations and Maintenance Considerations for Geometric design D-7 Increased liability, cost/reduced safety Categories assigned are indicative only and will need to be assessed for each overall design. May increase or reduce criteria Reduced liability, cost/increased safety Design Element Geometric Design Options C ap ita l C os t Li fe -c yc le Ef fic ie nc y M ai nt en an ce Sa fe ty O w ne r Li ab ili ty Examples Horizontal/Vertical Alignment Horizontal Alignment Avoid sharp horizontal curvature (small radii) which may incur more maintenance from loss of surface friction, poor drainage from melting snow, and run-off-road crashes. Where sharp curvature is unavoidable, consider wider lanes, paved shoulders, and speed reduction measures in advance of the curve. Address issues of pavement rutting and polishing that might affect drainage. Curves also require more signage and other appurtenances. Consider future tort liability if there is a maintenance issue. SSD Increase sight distance on approach to features needing frequent or regular maintenance (bridges and culverts, intersections with traffic control devices). Consider increased sight distance by bridge areas to accommodate annual or routine bridge maintenance. Vertical Alignment Avoid placement of features needing regular maintenance beyond the crest of a curve. If this is unavoidable, provide additional shoulder width or pull-off area. Additional shoulder width or pull-off area can be used for safe parking of maintenance vehicles. Avoid sag vertical curvature in superelevation transition areas or with limited cross slope. Cross slope, superelevation, and vertical curvature can combine to have difficult to understand effects. Combination of design elements may cause water ponding and poor subsurface drainage, both of which can damage the pavement. Geometric design should incorporate the checking of pavement contours prior to finalizing the three-dimensional alignment. Drainage Develop and refine vertical and horizontal alignments of culverts so that inlets and outlets are close to existing channels. Helps to prevent sediment or erosion. Consider future pavement resurfacing requirements when establishing vertical clearances and designing elements such as inlet grates and manhole covers. Other Investigate geology and geotechnical features to avoid or minimize potential maintenance problems. Investigate rock slides, highly erosive or expansive soils, and unsuitable materials. Maximize southern exposure in mountainous and hilly areas and allow space with proper drainage for dumping or storing plowed snow. Southern exposure minimizes snow and ice accumulation. Cross Section Traveled Way Widen pavement 2 to 3 feet to reduce edge stress. Consider also shoulders tied into travel lane pavement. Shoulder Provide at least 12-foot shoulders for maintenance vehicles to operate without affecting traffic. Where narrower shoulders are necessary, provide intermediate wider turnout locations. Reduces access costs and provides safe access. Assess width of right of way versus steeper slopes or retaining wall. Provide alternative access routes to avoid need to use lane or shoulder. Provide longitudinal sidewalks/shared used pathways between features to allow safe access. Provide pull-off areas for maintenance vehicles where full shoulders are not present. Make provision on roads without any existing shoulder or designed pull-off area. Provide paved areas adjacent to shoulders, particularly for frequently maintained features, e.g., signal controllers at intersections. Drainage Consider alternative drainage designs. Avoid manhole covers within lanes and shoulders Table D-4. Examples of geometric design decisions. (continued on next page)

D-8 A performance-Based Highway Geometric design process Use a movable barrier to provide access. Improves maintenance access, but may present other issues. Increase width. Provide wider medians to eliminate the need for glare screens and to reduce their construction and maintenance costs. Improve maintenance worker access to median. Improve maintenance access and safety where necessary to be narrow. Avoid the use of unpaved narrow medians as maintaining grass areas is difficult, and costly. Use concrete median barriers in narrow medians to redirect vehicles parallel to the traveled way. Minimize features in medians. Avoid manholes in shoulders and medians. Lateral Offset Move work to locations remote from traffic. Place cabinets near right-of-way line. Provide benches in higher cut slopes. Collect debris, slow runoff, and collect water from slope pipes. Access for maintenance vehicles should be provided. Reduce roadway side slope ratios and ditch profile grades. Flatten side slope embankments. Minimizes erosion potential and makes maintenance operations easier. Conduct an engineering analysis to compare embankment sections having flat slopes and wider right of way with sections having steeper slopes or retaining walls, or both. Drainage Design roads with ditch shapes that can be maintained Ditch bottoms should be wide enough to be maintained with common grading equipment. Sound Walls Provide doors in the wall to access from behind Roadside Design Access Avoid access locations where lane departures are more likely when locating features requiring regular maintenance roadside appurtenances. Avoid locating a cabinet or sign at end of lane merge tapers or at narrow shoulders. Provide alternative access routes to avoid need for maintenance vehicles to close a lane or shoulder. Provide cut-throughs at interchanges and small lengths of gated access road. Provide pull-off areas for maintenance Locate pull-off areas adjacent to features to vehicles. be maintained. Reduce the amount of hand trimming required and eliminate places that are difficult for mower access. Select low maintenance and low growth landscape features. Clear Zone Avoid obstructions within the clear zone. Placement of appurtenances away from the traveled way, especially in areas on the outside of curves. Location of signage. Move sign positions away from trees or vice versa. Remove trees in advance of signs to avoid the need for continual trimming. Place lighting columns on bridge approaches. Consider placing lighting columns on approaches to bridges rather than on the bridge to remove the need to access them from the bridge itself. Minimize features on the roadside within complex highway geometry. Increase distance of the roadside features to traffic within a complex interchange. Lateral Offset Provide inlets in grass medians and in curbed sections. Eliminates ponding. Combine inlets with curb openings if debris accumulation is a problem. Co-locate features at locations where maintenance is safe and convenient. Weather stations, control and power cabinets, combine concrete barrier, glarescreen, lighting base, drainage. Place roadside appurtenances to optimize maintenance access. Move away from the roadway. Reduces need for barriers and guardrails. Locate signs so that guardrail requirements are minimized. Ensure access is easily and safely available, visibility is not inhibited, conflict with landscaping and other highway elements is avoided, and vegetation control operations are not hampered. Lateral Offset Avoid placing signs in the ditch. This might impede drainage, make mowing more difficult and result in erosion or siltation around the sign support. Consider riprap around sign supports to minimize the need for herbicidal treatment. Fixed Objects Avoid the use of roadside barriers if the fixed object can be appropriately relocated or eliminated. Roadside fixed objects should only be used where alternatives are impractical. Median Median openings for barrier or closed medians. Improves maintenance access, but may present other issues such as the need for barriers and signage to prevent driver abuse. Table D-4. (Continued).

Operations and Maintenance Considerations for Geometric design D-9 Key Geometric Design Options Discussion There are a number of key decisions required during the geometric design process that are included in the previous table. This section explores the options in more detail and proposes an overall approach that would serve to assist in geometric design process communications and post-design requirements. O&M Strategic Plan It is recommended that a holistic approach be used from the outset of design that draws together inputs from the designer and experienced maintenance personnel in the form of an O&M Strategic Plan. The O&M Strategic Plan documents the O&M design decisions made throughout the design process, with an approach that assesses, at each design process step, whether the overall design facilitates future O&M activities (Table D-5). Producing an O&M Strategic Plan requires effective communications throughout the design process, beyond the geometric design. It is a document that, from the outset of a project, can inform the production of an asset management plan for the facility and help to address legislative requirements, e.g., MAP-21. NCHRP Report 349 The recommendation concerning O&M analysis and strategic planning complement the findings of NCHRP Report 349. This NCHRP report recommends that maintenance be con- sidered from the commencement of initial location studies, and that this consideration should be continued throughout the design process. Decisions regarding alignment have a substantial impact on O&M requirements and are some of the earliest decisions that need to be made. The number of intersections or interchanges along a route, or the decision that the route should go around an obstacle, under it, or over it has profound capital, O&M cost and safety implications. The costs for the construction, maintenance and operation of each choice of route and associated Step 1 Define the Transportation Problem or Need Preliminary risk assessment and decisions regarding alignment Step 2 Identify and charter all project stakeholders Identify stakeholders for O&M Strategic Plan input Step 3 Develop the project Scope Accounts for key project O&M risks Step 4 Determine the project type and design development parameters Step 5 Establish the project’s context and geometric design framework—project evaluation criteria Establishes basis for O&M geometric design options Step 6 Apply the geometric design process and criteria Make and document assessments of O&M geometric design alternatives using CBA, LCCA, and other methodologies in order to make informed trade-offs Step 7 Designing the geometric alternatives Review the overall project risks and select the most appropriate geometric alternative Step 8 Design decision making and documentation Continue to refine the design and document assessments and trade-offs, guided by risk assessments Step 9 Transitioning to preliminary and final engineering Step 10 Agency O&M database assembly Production of final O&M Strategic Plan Step 11 Continuous monitoring and feedback to agency processes and database Reuse the approaches for similar projects and incorporate feedback from O&M staff Table D-5. O&M Strategic Plan development during geometric design process.

D-10 A performance-Based Highway Geometric design process worker risks should be assessed using similar parameters. This can be applied across locations and different types of facilities. Use of ITS The use of intelligent transportation systems (ITS) requires a major commitment by agencies to provide the necessary resources to safely and efficiently operate a highway. Increasingly in urban areas it is often the only way by which to make expansions or new construction feasible to provide the necessary capacity. Additional considerations are needed regarding potential operational failure, and risk, e.g., during a power outage. Roadside Geometry Versus Roadside Alternatives Roadside appurtenances also demand a large share of maintenance budget. Traffic, vandalism, animals, and atmospheric conditions can cause damage to these elements. Their maintenance and repair are labor-intensive. Substantial cost can be saved if they are designed and built to be safe, durable, and easy to maintain. Maintenance problems related to drainage are costly expenditures. Constant attention must be given to controlling erosion in ditches, cleaning culverts and stormwater systems, repairing eroded and scoured outlet areas, controlling corrosion, and repairing damage due to frost and clogging. One of the principal trade-offs will be the decision about the costs and benefits of the alterna- tive designs that reduce right of way and land acquisition costs by incorporating steeper slopes, walls, or require more physical barriers. The amount of right of way needed should reflect the analysis of what might be considered necessary for a least cost maintenance design. The use of decision-making tools and development of a life-cycle cost model will assist in design decision making. There may be specific concerns that preclude some options, but an overall assessment, including a CBA can assess design alternatives and inform the process. Owner Liability O&M is a DOT function and a responsibility that only increases with an expanding network. With any increase in maintenance needs comes an increase in liability for the responsible agency. To reduce this liability, designs with reduced or low maintenance and limited worker exposure should be the ultimate goal. In addition to a maintenance perspective review during project design, the development of a specific list of design practices may be appropriate to address maintenance needs in a particular area. Agencies need to recognize the liability that O&M brings and prioritize the mitigation of key risks accordingly using risk management approaches. While mitigation measures may be costly, the cost of not implementing measures that are critical to health and safety are often much higher. The life-cycle cost would have to be grossly disproportionate to the benefit for it to be ignored. Further Research and Study Areas that would benefit from further research and study include: • Costs and benefits of critical design options to establish dimensional criteria and guidance, including examples. • Statistical analysis of maintenance personnel incidents and development of substantive crash prediction methods to guide the geometric design of alternatives that affect work zone safety, enforcement, and incident management options. • Better understanding of the short- and long-term risks concerning the O&M of facilities that use ITS technology.

Operations and Maintenance Considerations for Geometric design D-11 References CIRIA Report C686, Safe Access for Maintenance and Repair. Guidance for Designers, 2nd edition, 2009. http://apps. trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=373. FHWA LCCA model—https://www.fhwa.dot.gov/infrastructure/asstmgmt/lccasoft.cfm. Interim Advice Note 69/15, Designing For Maintenance (April 2015), Highways England Roads in Hertfordshire: Highway Design Guide 3rd Edition, Section 2: Highway Layout and Strategies, Chapter 7: Design for Maintenance. Maintenance Considerations in Highway Design, Road Engineering Journal, Copyright © 1997 by TranSafety, Inc. Ceran, T. and R. B. Newman. NCHRP Report 349: Maintenance Considerations in Highway Design. Transportation Research Board of the National Academies. Washington, D.C., 1992. The Institute of Asset Management, Asset Management—An Anatomy, Version 2, July 2014, www.theiam.org Washington State Department of Transportation, Design Manual M 22-01.11, July 2014.