The user is responsible for applying engineering judgment in interpreting and using program results and also obtaining the most suitable surface/terrain to be used in AutoTURN Pro. Familiarity with the software and its limitations is therefore important to ensure that the results produced by the software are applied appropriately.

Use of Design Guidelines

AutoTURN Pro is not intended to be a source for design information. The software must be used in conjunction with the most currently available design guidelines for the local jurisdiction. Where vehicle information is not specified in the design guidelines, logical assumptions have been made and noted for each vehicle (see Tools -> Vehicles -> Vehicle Information).

3D simulations can only be created with 3D capable vehicles. To determine whether or not a vehicle is 3D capable, click Tools -> Vehicles -> Select Current Vehicle. The Vehicle Profile Data graphic will display in the lower right corner of the preview area if the vehicle has profile data specified for it.

When designing/analyzing with AutoTURN Pro, users must understand that the vehicles are created using idealized values to represent as closely as possible the outlines of real vehicles. The characteristics of the vehicles, such as the articulation angles, are also represented by idealized values.

Realistic Vehicles

Realistic vehicle models based on realistic drawings are supposed to be used only for aesthetically pleasing representation of vehicles in simulations. In the actual calculations and analysis functions, AutoTURN Pro employs the parametric analytical vehicle models based on the part configuration and vehicle dimensions. Therefore, for vehicle customization, it is recommended to copy or create a vehicle based on an existing one, and then edit it to suit the design criteria (see Tools -> Vehicles -> Copy Vehicle and Tools -> Vehicles -> Create New Vehicle).

Terrain - Surface and Mesh Objects

Note: This functionality is only available in AutoTURN Pro.

The user is responsible for providing terrain objects to be used in AutoTURN Pro. There are a variety of surface and mesh type objects available in AutoCAD/BricsCAD/ZWCAD and MicroStation. AutoTURN Pro only supports surface/mesh objects which meet the following criteria:

In AutoCAD/BricsCAD/ZWCAD:

• A Polyface Mesh cannot have faces that have more than three visible or invisible edges. None of the faces can overlap with other faces.
• Each face of a Polygon Mesh must have four edges.
• A Polygon Mesh cannot have the fit/smooth feature applied - that is, only discrete vertices are supported.

In MicroStation:

• A Mesh cannot have faces that have more than three visible or invisible edges. None of the faces can overlap with other faces.
• Each face of a Mesh must have four edges.

AutoTURN Pro has not been designed to handle extreme changes in terrain. Undesirable output may result when generating/placing 3D simulations on terrains with extreme changes in elevations over short distances.

Interpretation of Program Results

AutoTURN Pro is primarily a kinematic model, meaning that it does not account for centripetal forces or road surface conditions other than dry pavement. A simple center of mass algorithm is incorporated in the software to ensure that reasonable output is obtained with respect to varying terrains.

AutoTURN Pro produces geometrically idealized results that may be difficult to replicate exactly under actual field driving and road conditions. A successfully run AutoTURN Pro simulation does NOT suggest that all drivers can follow the defined path in real conditions, NOR does it imply that other drivable paths between the desired start and end positions are not possible.

For the above reasons, AutoTURN Pro results should be used conservatively, with ample allowances added for clearances between vehicle tire track or swept path envelopes and road edges or obstructions.

Turn Speeds and Minimum Turning Radii

Turn limitations for standard design vehicles are generally based on the minimum turn radius as specified in the design guidelines for each jurisdiction. These are generally intended for speeds of less than 15 km/h (about 10 mph).

For AUSTROADS vehicles, turn limitations are based on the absolute minimum radii, which are for speeds less than 5 km/h.

Unusual Conditions

If non-standard vehicles, roadway surfaces other than dry pavement, or other unusual or non-standard conditions are used, AutoTURN Pro may produce inaccurate results. Caution is advised when dealing with the following conditions for which program results have not been verified:

• Speeds greater than 15 km/h (about 10 mph) where tire slippage and inertial forces become significant.
• Icy or otherwise slippery road surfaces because they tend to produce less tire tracking than dry road surfaces.
• Custom vehicles with multiple-axle bogeys consisting of three or more axles per bogey (as in heavy load movers).
• Vehicles where the ratio of the spacing between the fixed axles in a group to the wheelbase (the distance between axle groups) is 0.5 or more.
• Vehicles having more than four tires per axle.
• Vehicle parts with steerable rear axles.
• Vehicle combinations with multiple tractors.
• Vehicle combinations consisting of tractors with four or more trailing units.
• Rugged terrain / off-road condition.

It is highly recommended that you obtain as much turning information as possible for non-standard vehicles from manufacturers and other sources so as to be able to verify and draw conclusions about AutoTURN Pro’s results.

Tight Maneuvers with Standard Vehicles

The standard design vehicles provided with AutoTURN Pro have turn limitations derived from the turning templates contained in the Design Manuals published by the corresponding jurisdictions (see Vehicle Library Source Documents). The primary purpose of these design manuals is to provide guidance for typical road design conditions.

Consequently, in some cases the standard vehicles may have turning circles that are too large for situations where tight maneuvering is required, such as in loading areas or parking facilities. In these cases, it may be necessary to create user defined vehicles and provide turn limitations that allow the tighter, more realistic minimum turning circles. In AutoTURN and AutoTURN Pro this can be accomplished by creating a vehicle based on a design vehicle and setting higher values for the steering lock angle and articulating angles (see Tools -> Vehicles -> Copy Vehicle and Tools -> Vehicles -> Create New Vehicle).

CAUTION! The user must set steering lock angles that reflect the turn limitations of the specific vehicle being considered. Actual field measurements or manufacturers data should be used. Use of arbitrary angles will lead to misleading results.

Acceleration

AutoTURN Pro does not consider vehicle acceleration or deceleration. When simulations are generated from a stopped position, or to a stopped position, the vehicle is assumed to reach its final speed, or come to a stop, in a short enough distance that it can be ignored when determining the turn radius.