A Performance-Based Highway Geometric Design Process (2016) / Chapter Skim
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D-1 This appendix identifies the typical decisions that could be made during the highway geometric 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.
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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.
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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 crosssection dimensions are being set.
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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.
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Operations and Maintenance Considerations for Geometric design D-5 Figure D-1. Example of LCCA model from FHWA -- RealCost 2.1 Switchboard.
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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 lifecycle cost.
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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)
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D-8 A performance-Based Highway Geometric design process Use a movable barrier to provide access. Improves maintenance access, but may present other issues.
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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.
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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.
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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.
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