Turn penalty files are used for incorporating turn delays in highway skimming/assignment. These files define the turning movement, the penalty set and the penalty value in time units (a negative value is used for turn prohibitions). Turn penalty files are ASCII files with 4 four columns of data: From Node, Through Node, To Node, Penalty Set and Penalty Value. Below is an example
437 443 599 1 0.2437 443 993 1 0.2437 443 1235 1 0.4599 443 437 1 0.2599 443 993 1 0.4599 443 1235 1 -1.0993 443 437 1 0.4
Users can create a turn penalty file by using any text editor and visually identifying the nodes and direction of turn for each turning movement, from a highway network. Cube network editor window also provides an excellent interface for coding turn penalties. Both these methods involve coding turn penalties each node at a time. This could be time consuming. To avoid this manual coding and save some time coding each turning movement, user’s can use the attached Voyager script to output a turn penalty file, which has left and right turning movements with constant penalties. This script uses the NETWORK program and the topology functions to code left and right turn movements in the network. It works by identifying the upstream link for each link, and calculates the angle from the upstream link. If the angle is greater than 45 deg and less than 135 deg, the turning movement is coded as left turn. If the angle is greater than 225 deg and less than 315 deg, the turning movement is coded as right turn. The angles might be more accurate if the input network is a shape network compared to a stick network.
Users have to update the following variables before running the script for their network.
<left turn penalty>
<right turn penalty>