The Dynamics settings limit the turning radii for comfort at higher speeds. The automatically generated values are based upon published documents. To activate the settings, select Limit Turning For Dynamic Effects. You can use the supplied values from one of the references, or set your own limiting values.
to use values from one of the available sources, select the source in the Recommendations From list and select the Design Context. The units used for each design context are indicated with (M) or (US) in the context name representing metric and US customary units respectively.
The recommended and calculated fields change to reflect your selections. The distance data are presented in drawing units and the speed in the same units as your design speed.
If you do not want to use one of the recommended values, clear the Use Table Value check box and enter the preferred value in the edit box on the left.
Side Friction Factor (f) is the ratio of the force parallel to the road surface and the reaction perpendicular to the road surface; the recommended values are all based upon comfort limits rather than physical skidding limits.
Superelevation (e) is the slope of the road surface at right angles to the direction of vehicle travel. It is expressed as a factor, so 2% super elevation should be entered as 0.02.
Minimum Applicable Speed (V) is the lowest speed listed in each table.
Minimum Turn Radius (R) relates to the current forward design speed, and the values used change as you vary the speed. They do not apply in reverse. Vehicle Tracking will use the value listed in a table if the current forward design speed is within 0.5 km/h. If the design speed is outside this tolerance, then the limiting radius will be calculated direct using the curve formulae relevant to the design publication and context.
The equation used for limiting values of e and f is as follows:
R = V2/127(e+f)
Where
If the sum of superelevation and side friction factor is zero, the minimum turn radius will not be calculated.
The radius relates either to the outermost wheel track, the innermost wheel track or the centre of the steered wheels. Select it from the drop down list box. The defaults for this field vary according to the selected table and are based upon advice from AASHTO representatives. If you select Radius Is Offset From Outermost Wheel Track or Radius Is Offset From Innermost Wheel Track, then the calculated limiting wheel angle is based upon the path the vehicle must steer to keep the wheels just within the outer lane marking or just outside the inner lane marking respectively. In reality you will probably want to model the vehicle travelling some distance away from the lane marking to avoid collisions with vehicles in adjacent lanes or oncoming vehicles. Enter the clearance between the vehicle wheel envelope and the lane marking in the edit box provided.
Vehicle Tracking will prevent a vehicle from using the limiting radius if it is lower than its design capabilities.