Visibility Check - Check Profile Sight Distance

Last updated: 2022-08-30

Overview

This tool checks for sight distance obstructions along a profile utilizing input parameters for object height and required stopping, decision or passing sight distance. The tool provides options to create a report, an available sight distance profile and sight lines in the profile view.

The eye height used is 3.5 feet above the analyzed profile. The tool can be used to analyze projects based on the standards located in FDM 11-10-5.1.1 Stopping Sight Distances (SSDs); Decision Sight Distances (DSDs) and FDM 11-10-5.1.3 Passing Sight Distances.

Warning: This tool only analyzes a given profile and does not account for roadway geometry or obstructions created by the surrounding proposed or existing topography. Therefore, the actual sight distance may not be determined by using the Check Profile Sight Distance tool. See Stopping sight distance - 3D analysis for information on performing a three-dimensional analysis.

Using the Command

WisDOT Design tab > Analyze panel > Visibility Check dropdown > Check Profile Sight Distance

The tool can also be accessed from the command line: DOTCheckProfileSightDistance.

Profile Sight Distance dialog box

Tooltips are available for all inputs and controls.

Sight Lines

  1. Profile - existing or proposed profile to perform analysis along.
  2. Start Station
    1. Enter start station or
    2. Use button to select start station from drawing
    3. Default is profile start station or profile view start station, whichever is greater.
  3. End Station
    1. Enter end station or
    2. Use button to select end station from drawing
    3. Default is profile end station or profile view end station, whichever is lesser.
  4. Reverse
    1. Swaps start and end station
    2. Automatically switches the direction of travel for Travel Direction for Layer Assignment (12)
    3. Output report and profile should be renamed if the analysis direction is reversed
  5. Check Increment (ft) - The interval along the alignment to perform the sight distance analysis
  6. Sight Distance (ft) - The required sight distance. See FDM 11-10-5.1 Sight Distances
  7. Object Height - Height of object to be seen by the driver. Text in parenthesis is included in the sight line layer name.
    1. 24 in (SSD), Stopping Sight Distance
    2. 24 in (DSD), Decision Sight Distance
    3. 42 in (PSD), Passing Sight Distance

Output

  1. Create Report - check the box to create a csv file of the results
  2. Create Profile - check the box to create a profile that represents the sight distance (y-axis) based on station location (x-axis)
  3. Create Sight Lines - check the box to draw sight lines based on the Check Increment and Sight Distance values.
  4. Travel Direction for Layer Assignment - NB, SB, EB, WB are included in the layer naming for the created sight lines

Dialog box controls

  1. Refresh - refreshes the dialog after switching to a different active drawing or making changes to the current drawing. The dialog box can remain open while switching between drawings.
  2. OK - runs the command, a progress bar appears while calculations are performed
  3. Close - closes the dialog box
  4. Help - opens the Civil 3D Knowledge Base homepage

Output

Report

See example report for report format.

The listed sight distance values will not exceed the required sight distance entered in the dialog. Longer sight distances may be available based on the characteristics of the analyzed profile.

The note "Surface data missing along path. Results may not be accurate." is included at locations where surface data is missing along a surface profile analysis.

Profile

The sight distance values along the y-axis will not exceed the required sight distance entered in the dialog. Longer sight distances may be available based on the characteristics of the analyzed profile.

A profile view must be created to see the sight distance profile.

Sight Lines

Behavior

Two dimensional lines are created within the analysis range set by the Start and End Station.

From:

Station: Check Increment station location

Elevation: 3.5 feet above the profile elevation located at the given Station

To:

Station: End station location is determined by the sight distance reported along the Alignment from the starting Check Increment station location.

Sight distance is the distance along the Alignment throughout which an object of specified height is continuously visible to the driver.

S = Sight Distance (feet)

If profile data DOES NOT exist at the analyzed sight distance, a sight line is drawn that is truncated to the profile data limits.

Elevation: Object Height above the profile elevation located at the given Station

Labels

Each sight line is labeled at the bottom of the profile view with the sight distance at that location.

Distance labels have an asterisk next to them to indicate that the tool detected missing profile data within the sight distance range. This can occur when a surface profile has gaps and near the end of a profile analysis range.

Note: Sight distance adjustments for roadway grades is not included in this tool (See Table 3-2, page 3-6, 2018 AASHTO GDHS).

Layers

Each sight line is an AutoCAD Line object. All of the sight lines are combined into an AutoCAD Group object. This allows for the selection of all the sight lines in order to delete, hide or isolate them at the same time, while still maintaining the flexibility of layer control on the lines.

If an individual element within the group requires a manual edit, set the PICKSTYLE variable to 0. This makes each element in the group selectable. When editing is complete, set the PICKSTYLE variable back to 1.

The tool creates the following layers (based on input parameters). If the layer already exists, then that layer will be used.

Layer naming format:

SIGHT_ < analysis type > _ < Travel Direction >_ SightDist < Met/Reduced > _ < Object Height > _ObjHt

  • SightDistMet = required sight distance has been achieved (layer color is green)
  • SightDistReduced = required sight distance has not been achieved because of a profile obstruction (layer color is red)

Example layer names:

  • SIGHT_SSD_NB_SightDistMet_24in_ObjHt
  • SIGHT_SSD_NB_SightDistReduced_24in_ObjHt