Own Expression

You can create your own custom expression for routing. 

This is useful when not using ITN or Open Roads data (or you do not want to route using either the shortest distance or ITN Road Speeds).

Select Applications > Routing Tools > Settings > Own Expression.

Use either the (1) Speed-based expression functions to build an expression for a specific overlay or use the (2) Routing expression option to enter your own expression directly.

1. Speed-based Expressions

To select the attribute on which to base your expression, first choose the overlay and the relevant schema column.

The Attribute can be interpreted in one of two ways: it either contains the actual speed to be used for routing or it contains a type.

Specify the type in the correct field with its associated speed:

The Play icon is a Windows ‘DataGridView’ control; the arrow shows which line is being edited or will be deleted if you hit the Delete key.

If needed, change the speed units.

Click Make Expression.

2. Routing Expression

Use this simple editor to enter your own routing expression. The simplest way to do this is to begin with a speed-based expression as above.

When you click “Make Expression” it is automatically loaded into the Routing Expression editor. Simply customise the expression to your needs.

• To save a custom expression, assign a name to the expression and click Save.
  
• To load a saved expression, select it from the drop-down box and click Recall.
  
• To delete a saved expression, select it from the drop-down box and click Delete.

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