Sight Distance

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Ribbon: Model Viewer > Analysis Tab > Sight Distance

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Introduction

Model Viewer contains some very impressive tools to calculate sight distances along a road and at intersections to ensure minimum design standards are met. Users can create their own sight criteria styles where parameters such as eye height, target height, and minimum sight distance lengths are specified. A grade correction table can also be setup to adjust the minimum sight distance based on the vertical grades along the road.

Visible and obstructed sight lines are displayed in Model Viewer and can be exported out as polylines into CAD.

When design changes are made to a road, the sight distance tools will update automatically when the auto update option is turned on. This allows the designer to check the suitability of a design as soon as vertical or horizontal changes are made to the road.
 

Information on navigation in the Model Viewer 3D environment is available when reviewing the Model Viewer command help.

Details

Once the Sight Distance command is selected, a separate tab on the ribbon is displayed, with command inputs as follows:

Sight Tables	Use the pick list to display any named Sight Table. Note: Sight Tables are created using the Manage Tables command button and the Intersection Check command button (see below).  In the Manage Tables command users specify the road, the driver and the target positions, the required sight distance and intervals to check.
Show Visible Lines	Toggle on/off the display of visible sight lines
Show Obstructed Lines	Toggle on/off the display of obstructed sight lines
Manage Table	This command allows users to create multiple sight distance checks, for multiple strings. The user can specify different sight criteria styles at certain locations along the road. A form will display with inputs as follows:   Manage Sight Tables Create named sight distance table criteria.  The right side is used for editing the created table.   [List of Sight Tables] Click on a named Sight Table to edit on the right   Add Table Create a new Sight Table.  Edit on the right.    Delete Table Delete a selected Sight Table. Sight Table This is where the Sight Table is edited    Name Name the Sight Table    Associated String Select a design string.  This is optional - if selected then grade correction can be applied to the sight distance results (if applicable)  Direction Select whether the sight distance is calculated:    Forward Radio Button  Sight distance is calculated in the direction of the alignment    Reverse Radio Button Sight distance is calculated in the reverse direction of the alignment Note: it is usual to check that sight distance is acceptable both directions along the road.  In Civil Site Design, separate checks are made for the forward and reverse directions Eye and Target Positions Select the driver and target positions.  Note: A Sight Criteria is applied at chaianges along the road.  The Sight Criteria can include the Driver and Target eye heights.  These are autoamtically added to the Set Position.    Eye Position This opens the Positioning Form for establishing the eye position (Driver position) Details on the inputs are as noted in the Positioning Form help link.    Target Position This opens the Positioning Form for establishing the eye position (Driver position) Details on the inputs are as noted in the Positioning Form help link. Sight Distance Checks      Sight Criteria The sight criteria style the sight line will utilise for calculation   Start Chainage Specify the start chainage for the Range being added.  Use the pick button to select from the drawing   End Chainage Specify the end chainage for the Range being added.  Use the pick button to select from the drawing   Inverval Specify the interval (distance along the string) to check sight distance.   Add Range Adds sight checks in the list, applying the sight criterial over the start/end chainage range at the specified intervale  [lList of Sight Checks] Lists all sight checks to be applied for the selected Sight Table.  Click on the ... button to edit the Sight Criteria.  Add Check Form will display. Type in a specific chainage to add to the list, using the Sight Criteria selected.  Override Selected If one or more entries are highlighted in the list, the selected Sight Criteria will be applied to the highlighted entries  Delete Check Delete the highlighted entry/ies in the list Delete All Clear the entire list (remove all sight checks) Close Exit the form
Sight Criteria	Establishes how the sight distance should be applied, as well as setting colours for visible and obstructed lines.  A form will display with inputs as follows:   Criteria Name A list of all available sight criteria styles are listed, Users can create a new criteria style by pressing . Criteria styles can be deleted by pressing Design Speed Specify the design speed (this value will have no affect on calculations) Type Specify the sight distance check type (this value will have no affect on calculations) Minimum Sight Distance Specify the minimum sight distance used when this sight criteria style is assigned to a sight line Grade Correction Click here to open a new form to apply grade corrections based on the longitudinal slope of the road. The software will intelligently read the vertical profile of the road and apply the sight distance length adjustments as specified. Inputs are as follows:   Use Grade Correction Table Adds the values to the Minimum Sight Distance, based on the Grade input and the Correction value. Upgrade Establish changes to the Minimum Sight Distance based on uphill grade   Grade 1- 4 Type in grades (%)   Correction Type in a distance to add to the Minimum Sight Distance value.  Positive to increase and negative to decrease. Downgrade Establish changes to the Minimum Sight Distance based on downhill grade   Grade 1- 4 Type in grades (%).  Use negative values for the downhill grades   Correction Type in a distance to add to the Minimum Sight Distance value. Positive to increase and negative to decrease. Apply Apply and exit. Eye Height Specify the eye height (start location for the sight line) Eye Offset Specify the eye offset (start location for the sight line) Target Height Specify the target height (end location for the sight line) Target Offset Specify the target offset (end location for the sight line) Visible Sight Lines Set display for visible sight lines   Colour Click on the colour swatch to open a colour selection form.  Click OK to select the new colour.   Lineweight Type in an integer for the lineweight to apply. Obstructed Sight Lines Set display for obstructed sight lines   Colour Click on the colour swatch to open a colour selection form.  Click OK to select the new colour.   Lineweight Type in an integer for the lineweight to apply. OK Apply and exit. Cancel Exit the form without saving
Intersection Check	This command allows users to create named sight distance checks at intersections.  The user can specify different sight criteria styles to apply in each direction along the main road.. A form will display with inputs as follows:   Manage Sight Tables Create named sight distance table criteria.  The right side is used for editing the created table.   [List of Sight Tables] Click on a named Sight Table to edit on the right   Add Table Create a new Sight Table.  Edit on the right.    Delete Table Delete a selected Sight Table. Intersection Sight Table This is where the Sight Table is edited    Name Name the Sight Table Main Road Setup the main road details   Alignment Select the alignment for the Main Road String   Intersection  Type in the Chainage of the intersection, or use the pick button and select from the drawing   Interval Distance along the main road to apply checks for the sight distance from the side road.   Use sight distance value from Criteria Style Select whether the software uses the minimum sight distance length from the sight criteria style specified, or by using the distance to point b and point c along the main road. Users can specify the chainage for point b and point c if this option is ticked off. Side Road (Vehicle Position)     Setup Position This opens the Positioning Form for establishing the side road driver position Details on the inputs are as noted in the Positioning Form help link. Start Target (Point B)     Setup Position This opens the Positioning Form for establishing the position of a driver approaching from the left of the side road driver Details on the inputs are as noted in the Positioning Form help link.   Chainage Note: this field will be disabled if Use sight distance value from Criteria Style is ticked on Use the 'pick' icon to select the intersection location from the drawing.   Criteria Style Select the sight criteria style used when computing sight lines for a driver approaching from the left of the side road driver. End Target (Point C)     Setup Position This opens the Positioning Form for establishing the position of a driver approaching from the right of the side road driver Details on the inputs are as noted in the Positioning Form help link.   Chainage Note: this field will be disabled if Use sight distance value from Criteria Style is ticked on Use the 'pick' icon to select the intersection location from the drawing.   Criteria Style Select the sight criteria style used when computing sight lines for a driver approaching from the right of the side road driver. Close Exit the form
Planar Check	The planar check expands on the idea of point-to-point sight distance, by instead allowing the user to set a rectangle to 'view' at the minimum sight distance, and to provide feedback on the percentage visibility to this rectangular area. This command relies upon the user having completed Sight Distance check/s - the eye position, target position (x,y and surface) and sight distance are used to calculate the visibility. See the Planar Check for details on the inputs and outputs for this command.
Report	Users have the option to display the results of the sight distance check in a table format. This table will update dynamically as the sight distance command is computed. All information regarding the sight lines used as part of the compuation are listed, Users can filter the list by specifying a chainage range and the display of visible and obstructed sight lines can be toggled on/off. The report can be outputted to a table in CAD or a CSV file. Once selected, the following form will display Chainage Establish report extents and compliance to display   Start Start chainage/station to commence report   End End chainage/station to finish report   Show Visible Toggle on/off the display of the visible sight lines   Show Obstructed Toggle on/off the display of the obstructed sight lines   Report Settings This will open up the Report Settings to enable configuration of the report output.  Inputs as follows: Table Title The title of the outputted table - used when outputted to a CAD table Table Style Specify the AutoCAD or BricsCAD Table Style Table Font Specify the font of the outputted CAD table Item List Spreadsheet view listing available items to report.  Tick items on/off to include in the report.  Width is used for any Table outputs to the drawing   Visible Toggle on/off the display of the item in the report   Name The name of the item (this cannot be edited by the user)   Display Name Specify the display name. This value is used when the report is outputted to a CAD table or CSV   Decimal Places Specify the decimal places of the value   Width Specify the column width for this item in the CAD table Save Settings Apply and exit. Close Exit the form without saving.   Table Output Output the report to a CAD table (either AutoCAD or BricsCAD table)   File Output Output the file to a CSV file. The file will automaticallty load (in the default program for the file type) once saved.
	Close the sight distance tab. Once this tab is closed, the sight distance check will no longer automatically update when Model Viewer is refreshed.