Evaluates the fastest path for a user-drawn roundabout. The results are calculated and drawn in the roundabout, and can be saved to a file.
The fastest path is the largest possible radii centerline path approximated based on the critical offsets (median offset, edge offset, central island offset) for the through path or turn path (for more information on the fastest path, see Overview -> Fastest Path).Note:
For an example of how the Evaluate Fastest Path tool is used to generate the fastest path for a user-drawn roundabout, please play the Fastest Path on User-Drawn Roundabout tutorial (for information on how to play a tutorial, see Tutorials' Play).
Replace the central island, entry median, exit median, entry edge, or exit edge used to generate the fastest path. To replace an element, click X under the element you want to have replaced, click the Replace Selected Element button, and then pick the desired element in the drawing. The fastest path data will be updated accordingly.
Select this check box to set the Distance and Circulatory Roadway Width values.
Specify the distance from the inscribed circle diameter to the median offset (the fastest paths starting and end points). By default, TORUS calculates the minimum distance required to obtain each valid fastest path's starting and ending point. The distance value will not change the calculation of R1, R2, and R3; however, it will provide a smoother transition from the starting point to R1 and from R3 to the ending point.
Note:
Specify the width of the circulatory roadway in the roundabout.
The Circulatory Roadway Width value works in coordination with the Distance value, which is based on the inscribed circle diameter. TORUS does not have information on the inscribed circle diameter of a user-drawn roundabout, so in order to start and end the fastest path at a specified distance, the software calculates the inscribed circle radius by adding the radius of the central island (i.e. the circle element picked in the drawing) to the sum of the Circulatory Roadway Width and Distance values.
Specify the entry edge offset value. This is the distance from the entry-side right turn edge to the fastest path.
Note: The entry edge offset is used is for internal calculation only. TORUS generates the transition between the arcs using a spline to closely approximate the realistic travel path of a vehicle.
Note: All fastest path critical offsets are the minimum offsets from the edge to the fastest path.
Specify the exit edge offset value. This is the distance from the exit-side right turn edge to the fastest path.
Note: The exit edge offset is used is for internal calculation only. TORUS generates the transition between the arcs using a spline to closely approximate the realistic travel path of a vehicle.
Select this check box to have the friction factor added to the fastest path data table (separated from the speed values by a colon). The side or lateral friction factor is the coefficient of friction between the vehicle's tires and the road surface. The friction value is assumed to decrease as the speed increases. Values that TORUS uses for the lateral friction factor were determined based on 2004 AASHTO Exhibits 3-11 and 3-12.
Note: The friction values are specified in the Friction.csv file stored in the FrictionData folder located in the user data folder (see Installation -> General Installation Notes: Default User Data Location). Friction.csv is a comma delimited file which can be edited in any text or spreadsheet editor (e.g. Microsoft® Notepad or Microsoft® Excel). The first column refers to the speed in miles per hour, and the second column to the associated friction factor.
Button | Option | Click to... |
Insert Fastest Path Results Table | Have the fastest path results table placed in the drawing. After you click this button, pick a point in the drawing to specify the place for the fastest path results table. |
TORUS populates the fastest path results table with the radius and speed data on the approach legs for the fastest paths in the roundabout.
Displays the name of the entry approach leg.
Displays the fastest path speed values that ProductNameProductName%% performs the speed consistency check for each approach leg based on the following conditions:
V1 < V2 + L
V3 > V1 and V3 > V2
V5 < V1 and |V5-V4| < L
where L is the limit of the speed difference. To modify the speed difference limit, use Design Guidelines' Fastest Path Category: Speed Difference.
Displays the travel path critical radii:
Displays the speed difference value.
Displays the superelevation values used to calculate the fastest path data (see Leg Superelevation and Circulatory Superelevation).
Note: Certain columns in the fastest path results table will only display if the related options are turned on in Design Guidelines' Analysis Conditions Category.