AutoTURN Pro 11.0 Help
SmartPath Tools Overview
SmartPath Tools allow you to automatically generate a vehicle path and simulation. This is done on the fly by moving the mouse in the direction of travel.
The SmartPath Tools account for a vehicle’s speed and for lateral friction and superelevation.
The minimum turn radius of a generated path is determined from either the vehicle’s minimum turning radius as calculated from the steering lock angle, or from a minimum turning radius calculated from the vehicle’s speed, lateral friction and superelevation. The larger of these two radii is used.
Minimum turning radius as a function of speed, lateral friction and superelevation is calculated using the following AASHTO formula:
| Metric Units | English Units |
|
R = radius (m) V = speed (km/h) e = superelevation (m/m, e.g., 0.02 = 2/100) f = friction (e.g., 0.03) |
R = radius (f) V = speed (mph) e = superelevation (ft/ft, e.g., 0.02 = 2/100) f = friction (e.g., 0.03) |
Default lateral friction and superelevation factors used in AutoTURN Pro are based on AASHTO (2004) values. The default values can be overridden at the time a simulation is created.
AutoTURN Pro’s SmartPath Tools generate vehicle paths that account for the maximum rate at which the steering wheel can be turned by incorporating spiral sections into the generated path. The spiral sections transition the steering wheels between their initial angle and the angle required to turn toward the target point.
Steering wheel turn rate is determined from the lock to lock time and the vehicle’s speed.
Conservative lock to lock times are assumed for all standard design vehicles.
Reverse maneuvers are generally considered to be performed with single part vehicles and can not be carried out by vehicles with more than three parts. Lateral friction and superelevation are not accounted for in reverse maneuvers; however, the steering wheel turn rate is. Reverse maneuvers are carried out at 6 mph (10 km/h) or less, speeds at which these factors should be negligible.
Turn simulations created from pre-drawn paths do not account for speed, lateral friction, superelevation, or steering wheel turn rate.
Only forward maneuvers are possible with pre-drawn paths. Reverse maneuvers must be carried out using the SmartPath Tools.
The path must be created using either a series of connected lines and arcs, or a single polyline (for AutoCAD) or a single complex chain (for MicroStation). Splines (for AutoCAD) and B-splines (for MicroStation) are also supported.
