Roadway Cross-Section Reallocation: A Guide (2023) / Chapter Skim
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Chapter 8: Making and evaluating cross section changes
Chapter 8: Making and evaluating cross section changes
Pages 111-148
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From page 111... ...
Introduction NCHRP Research Report 1036 presents a decision-making framework for roadway designers, planners, and others seeking to identify, compare, evaluate, and justify context-based cross-section reallocations of existing urban and suburban roadway space for multimodal safety, access, and mobility. This report includes a spreadsheet tool to help with decision-making.
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• The "Step 3" sheets provide summaries of the decisions made and the results: – "Step 3A Cross-Section Summary" provides a visual before-and-after comparison of roadway cross sections. Figure A-1.
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. Print Results Documentation Edit Cross Section to Achieve Minimally Safe Design Input Project Information Step 1 Step 2A Step 2B Step 3 Edit Cross Section to Allocate Additional Space (if applicable)
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Figure A-3. Spreadsheet Tool Cell Shading.
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Step 1.1 – Existing Cross Section In Step 1.1, fill out the table to represent the project roadway's existing cross section (see Figure A-6)
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If those numbers change substantially along your project corridor, consider subdividing the project into sub-corridors with consistent width and applying this method to each of those sub-corridors. 38 The available right-of-way in feet Automatically calculated from Step 1.1.
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This information is provided here for verification and recorded to document existing and proposed cross sections. The minimum safe facility provided in the next step will automatically exclude street parking from the proposed cross section because it is not a required element for a minimally safe facility.
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Proceed to the next step to explore options to make up this difference. The base minimum safe cross section is presented here.
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The user has two basic categories of possible edits that can help the proposed cross section meet minimum safe requirements -- users can edit roadway characteristics or they can edit crosssection elements. Edit Roadway Characteristics The tool presents three options for fundamentally altering the roadway that will generally relax width requirements if the minimum safe cross section is not met (see Figure A-11)
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Figure A-10. Menu of Design Options.
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(a) With the existing condition of 30 miles per hour travel speeds and approximately 20,000 vehicles of daily traffic, the minimum bike lane requirements are a 6-foot-wide lane and a 2-foot-wide separation: 8 feet total per direction.
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(b) With the desired roadway speed changed to 20 miles per hour, the width requirements are instead a 5.5-foot-wide lane and no separation: 5.5 feet total per direction (a reduction of 2.5 feet per direction, or 5 feet total)
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(c) With a safe parallel facility identified, there is now no minimum width requirement for bicycle facilities on the project roadway: a reduction of 8 feet per direction (16 feet total)
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After changing elements, select the "GENERATE CROSS SECTION WIDTH" button to calculate whether minimum dimensions are met (see Figure A-12)
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Figure A-13. Example of edited cross section with two-way bike lane selected.
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For example, if the project adds bike lanes, this page provides a descriptive summary of the potential safety, economic, environmental, social, and mode shift effects of the bike lane addition. The impacts are typically qualitative with "low/medium/high" and "near-term/ long-term" descriptors to describe the magnitude and timeline of effects.
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For the existing cross section, press the yellow button to calculate the controlling downstream intersection and input the default D factor and K factor. You may edit these cells if you know the D factor or K factor or choose to use another downstream intersection type.
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B-1 Decision Support Matrix A P P E N D I X B
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High Positive effect: Bus reliability and travel times can be significantly improved, making transit a more viable and competitive option. In areas where congestion is low, adding a bus lane is likely to have insignificant effects.
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Narrow bike lanes Medium Adverse effect: If reduces width below minimally safe width or reduces the comfort of bicyclists, leading to less use and less expectation of bicyclist presence and behavior; reduced separation from motor vehicles can also lead to decreased visibility of bicyclists. Low/Medium Adverse effects: If the reduction decreases the comfort of bicyclists, the reduction causes a decrease in accessibility that affects local businesses and individuals' travel costs and options.
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Add bike lanes High Positive effects: Adding exclusive biking space leads to the increased comfort of bicyclists, which leads to increased use and expectation of bicyclist presence and behavior The Caltrans Local Roadway Safety Manual cites a 55% CMF for the addition of separated bike lanes and a 65% CMF for painted bike lanes. Medium Positive effect: The increase in accessibility affects local businesses and individuals' travel costs and options.
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Pedestrian Facilities Safety Economic Environmental Social Mode Shift Remove pedestrian facility High Adverse effects: May force people to walk in or along facilities dedicated to and designed for other users; likely also leads to reduced use from pedestrians and less expectation of pedestrian presence. Removes access for those requiring ADA facilities.
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Safety Economic Environmental Social Mode Shift Widen pedestrian facility Medium Positive effect: If it increases width above minimally safe width or ADA standard widths. Medium Positive effect: Increase in accessibility affects local businesses and individuals' travel costs and options and provides space that can be used to support area businesses (e.g., sandwich boards, bike parking, and benches)
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Low Positive effects: Reduces speeds and travel times, thereby reducing the propensity to drive. Widen travel lanes Medium Adverse effects: Unless existing lane widths were inappropriate for design vehicles.
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Adverse effect: If buses share a travel lane, decreased congestion can improve reliability and travel times, increasing attractiveness of transit, reducing the amount of induced demand. Medium Adverse effect: Impacts opportunities for placemaking: street crossings are longer, vehicle speeds and volumes are likely higher, induced demand can increase driving, negatively affecting health outcomes over time.
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Low Decreases motor vehicle access to businesses/services in areas where there are driveways/access points. Low Positive effect: Decreased capacity/motor vehicle access may lead to decreased volumes over time.
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Low Positive effect: Could improve sales receipts if people are more willing to shop as a result of sufficient pedestrian crossing opportunities (and perceived safety and comfort along a street)
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Medium Positive effect: Increased access to commercial uses, if managed appropriately, ability to serve for loading/unloading delivery vehicles, and may improve customer access (finding parking) for businesses without off-street parking.
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Project Type City staff has identified grant funding as the mechanism to advance this project, and the targeted grants would support a reconstruction project. Therefore, a proposed project could move curb lines.
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• Improve safety and comfort for people walking and biking, especially at major intersections. Existing Conditions and Cross Section Figures C-2 and C-3 show a site photo of the existing cross section and a schematic of the cross-section allocation.
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Existing cross section (visualization)
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Recommended bike lane and buffer widths.
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• Separated bike lanes on both sides • No street parking Figure C-6 shows that this proposed cross section leaves 5 extra feet of cross-section width. Because there is enough space to build the minimum safe facility, the City proceeds to Step 5 (recognizing that they may iterate on developing design options)
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This cross section includes • Two-way bike connectivity on the east side; • Extra space on the shared-use path shoulder, which can be used to taper the 6-foot-wide buffer at bus stop locations; • A 6-foot-wide median; and • An expanded sidewalk and buffer zone on the west side of the street. The proposed cross section shown in Figure C-8 "works," provided that two through lanes are sufficient to serve travel demand.
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Figure C-7. Cross-section 1 in Step 5.
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Step 6: Evaluate and Choose the Cross Section That Serves Your Community's Vision and Needs In this step, the City will compare its preferred cross section to the existing conditions. If desired, an additional comparison could be included to evaluate the potential effects of alternative proposed cross sections.
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