The user is responsible for applying engineering judgment in using and interpreting program results. Familiarity with the software is therefore important to ensure that the results produced by the software are applied appropriately. TORUS is intended for designing single-lane or multi-lane roundabouts with circular central islands and constant circulatory roadway widths. For multi-lane roundabouts, TORUS supports approach legs with a maximum of three lanes for both entries and exits.

Use of Design Guidelines

TORUS 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. For design guidelines developed from the vehicle envelopes design methods, TORUS uses design vehicle tire tracks as a basis for designing roundabouts. For design guidelines developed from the regional design methods, TORUS utilizes the design rules for those particular regions available at the time they were created as the basis for roundabout design. TORUS can use vehicles from the TORUS vehicle library including customized vehicles which can be imported from AutoTURN, or vehicles from the extended vehicles libraries which are available for purchase through Transoft Solutions.

Interpretation of Program Results

TORUS roundabouts created utilizing design guidelines developed from the vehicle envelopes design methods are derived from geometrically idealized vehicle paths that may be difficult to replicate exactly under actual field driving and road conditions. The layout of the idealized vehicle paths formulates the road edges of the roundabout design. The vehicle paths were implemented based on AutoTURN and research studies. A successfully run design movement 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 entry and exit approach legs are not possible.

Turn Speeds and Minimum Turning Radii

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

Limitations of AutoTURN should be considered where applicable.

For the above reasons, TORUS results should be used conservatively, with ample allowances added for clearances between vehicle tire track and road edges.