Roundabout Standard Editor: Fastest Path Analysis: Vehicle Paths

The roundabout must be capable of accommodating appropriate vehicles. This tab allows the user to define design vehicles.

Expand Fastest Path Analysis and click Vehicle Paths in the left hand pane. The Vehicle Paths page is displayed.

The Vehicle Path Radii frame displays the limiting radii at critical points on the roundabout and lets you define proximity warnings. As soon as the value in the HUD gets to within Warn % of the limiting value (max or min) it is displayed in orange. When it is less than the Min value or greater than the Max value it is displayed in red.

The Entry Path Radius is the radius of the path taken by the center of the front axle of the vehicle at entry to the roundabout, i.e. at or about the yield line.

The Circulating Path Radius is the radius of the nominally through path as it negotiates the center island.

The Exit Path Radius is the radius of the path taken by the center of the front axle of the vehicle at exit from the roundabout, i.e. at or about the exit line.

The 270 Degree Turn Path Radius is the radius of the path taken by the front axle of the vehicle as it performs a 270 degree turn. In fact this value is calculated for turn angle between 255 and 285 degrees.

The 90 Degree Turn Path Radius is the radius of the path taken by the front axle of the vehicle as it performs a 90 degree turn. In fact this value is calculated for turn angle between 45 and 135 degrees.

The Fastest Path Radius is the minimum radius on the fastest path through the roundabout.

The Vehicle Path Speeds frame displays the limiting speeds at critical points on the roundabout and lets you define proximity warnings. As with the radii, as soon as the value in the HUD gets to within Warn % of the limiting value (max or min) it is displayed in orange.

The Entry Path Speed is the speed that equates to the radius of the path taken by the center of the front axle of the vehicle at entry to the roundabout, i.e. at or about the yield line.

The Circulating Path Speed is the speed that equates to the radius of the nominally through path as it negotiates the center island.

The Exit Path Speed is the speed that equates to the radius of the path taken by the center of the front axle of the vehicle at exit from the roundabout, i.e. at or about the exit line.

The 270 Degree Turn Path Speed is the speed that equates to the radius of the path taken by the front axle of the vehicle as it performs a 270 degree turn. In fact this value is calculated for turn angle between 255 and 285 degrees.

The 90 Degree Turn Path Speed is the speed that equates to the radius of the path taken by the front axle of the vehicle as it performs a 90 degree turn. In fact this value is calculated for turn angle between 45 and 135 degrees.

The Fastest Path Speed is the speed that equates to the minimum radius on the fastest path through the roundabout.

Note: Where the standard does not specify a limiting radius or speed we have inserted the national or state speed limit so that the HUD’s have a limit against which to scale these critical design values. We have not used lower local speed limits because this could cause valid large radii (for example on roundabout exits) to display in red as excessive.

In all cases the Max and Min values represent the limiting values from the adopted design standard and the Default value will be used when the roundabout is first placed. A default value MUST be provided but Max and Min may be blank if there is no limiting value.