This category allows you to view and edit the approach leg and circulatory superelevation and fastest path parameters (for information on superelevation and fastest path, see Overview -> Superelevation and Overview -> Fastest Path respectively).

Design Guidelines' Fastest Path Category Dialog Box

In the dialog box, move the mouse pointer over the controls to view the associated tooltip and then reference the controls described below.

Note: For the purposes of describing the software, it is assumed that Right-Hand Traffic is selected under Traffic Direction in Design Guidelines' General Category. If Left-Hand Traffic is selected, the descriptions with references to a right/left turn path should be interpreted in the opposite direction.

Superelevation Defaults Section

Leg Superelevation

Specify the approach leg superelevation value. Based on the AASHTO values, the approach leg superelevation is usually assumed to be 2% (+0.02).

Circulatory Superelevation

Specify the circulatory superelevation value. Based on the AASHTO values, the circulatory superelevation is usually assumed to be -2% (-0.02).

Fastest Path Defaults Section

Speed Difference

Specify the speed difference value. TORUS uses the speed difference to check the speed consistency between the computed fastest path speeds at R1 and R2 on one side and R4 and R5 on the other. Based on the design standards, the default Speed Difference value is set to 20 km/hr and gets converted into the units specified in Program Settings' General Category dialog box.

Central Island Offset

Specify the central island offset value. This is the distance from the central island to the fastest path centerline.

Entry Median Offset

Specify the entry median offset value. This is the distance from the entry-side splitter island envelope or reference geometry to the fastest path.

Exit Median Offset

Specify the exit median offset value. This is the distance from the exit-side splitter island envelope or reference geometry to the fastest path.

Entry Edge Offset

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.

Exit Edge Offset

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.

Acceleration Rate

Specify the acceleration rate value. This is the time rate of increase in velocity with respect to magnitude or direction.

The acceleration rate is applied to the V3a calculation (see Overview -> Fastest Path).

Distance

Specify the distance value. This is measured from the inscribed circle diameter to the median offset. 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: By default, the Distance value is not used, and TORUS calculates the minimum distance required to obtain each valid fastest path's starting and ending point. Specify a value that is greater than the computed minimum distance to have the fastest paths start and end at a desired distance.

Deceleration Rate

Specify the deceleration rate value. This is the time rate of decrease in velocity with respect to magnitude or direction.

The deceleration rate is applied to the V1a calculation (see Overview -> Fastest Path).

Fastest Path Speed Arcs Section

Best Fit Arc Length

Specify the length of the R1, R2, R3, and R5 arc sections of the fastest path spline. This setting applies to the FDOT fastest path method only.