Design Guidelines for Horizontal Sightline Offsets (2019) / Chapter Skim
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71 A P P E N D I X B Users Guide for Reliability Analysis Tool This appendix presents a users guide for the spreadsheet-based tool that implements the reliability analysis model described in Chapter 5. The tool enables users to assess the horizontal curves with horizontal sightline obstructions present on the inside of the curve.
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72 Design Guidelines for Horizontal Sightline Offsets characteristics for the study site are entered in a table on the UserInput worksheet shown in Figure B-1. Figure B-1.
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Users Guide for Reliability Analysis Tool 73 Figure B-2. Selecting obstruction type and curve type.
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74 Design Guidelines for Horizontal Sightline Offsets • Curve radius: Enter the horizontal curve radius, in feet. • Curve length: Enter the horizontal curve length, in miles.
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Users Guide for Reliability Analysis Tool 75 Figure B-4. Horizontal curve and continuous obstruction data input.
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76 Design Guidelines for Horizontal Sightline Offsets direction of travel (adjacent to the horizontal sight obstruction) or the curve to the left in the opposing direction of travel (separated from the horizontal sight obstruction by the travel lanes in the primary direction)
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Users Guide for Reliability Analysis Tool 77 • Departure grade: Enter the roadway grade departing the vertical curve as a percent grade. Enter a negative value for a downgrade or a positive value for an upgrade.
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78 Design Guidelines for Horizontal Sightline Offsets object height of 3.5 ft, equivalent to driver eye height, or 4.0 ft. Either of these choices allows for some of the upper portion of the vehicle to be visible to an approaching driver.
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Users Guide for Reliability Analysis Tool 79 Figure B-10. Lane utilization data entry.
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80 Design Guidelines for Horizontal Sightline Offsets • SPF coefficients: The default SPF coefficients are shown on four "Default" rows. The functional form for all SPFs are shown in the equation above the coefficients.
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Users Guide for Reliability Analysis Tool 81 • Percent potentially affected: The percentage of total vehicles passing through a site that may be potentially affected by a crash-involved vehicle or a queue of stopped vehicles in the sight-restricted area is shown for each lane. • Time and date of last analysis: The date and time of the last analysis is shown and is updated every time the "Calculate" button is clicked.
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