Displaying isochrones and accessibility in PrT

With PrT, you have several possibilities to display the accessibility of network objects in the network:

With PrT isochrones, you can display the accessibility of each point in the network from one or several marked nodes, main nodes, or zones (Two-dimensional display of attribute values around point objects). Network objects can be origins or destinations of isochrone calculations. If the network objects are destinations, the isochrones specify the points from where the reference object can be reached within the same time.
You can display links according to their accessibility from currently marked nodes, main nodes, or zones (Setting the display for PrT isochrones at links).
You have the possibility to display nodes, main nodes, or zones classified according to their accessibility from currently marked network objects and use the Isochrones time PrT attribute for the classification (Displaying the accessibility of network object types according to classes).

Note: You can use all display types all at the same time.

1. If required, change the settings for isochrones in the Edit graphic parameters window (Setting graphic parameters for the display of isochrones).

2. On the Graphics menu, click Isochrones.

The Graphics tools (Isochrones) window opens.

3. Select the PrT tab.

4. Specify any further settings you need.

Element	Description
	Click the Reset symbol to delete the list of objects and all previously executed isochrones.
Network object type	Here you select the network object type from which you want to measure the distances. The following types are provided: Nodes Main nodes Zones
Transport system	Select the desired transport system.
Route choice criterion	The following path choice criteria are provided: t0 Run time in the unloaded network tCur Run time in the loaded network Impedance Impedance according to the assignment parameters Distance Link length AddValue 1...3 Attributes with user-defined values
Search direction	Here you specify the search direction of the isochrone. Network objects are origins If this option is selected, the isochrone displays the accessibility of each point in the network from the reference object. Network objects are destinations If this option is selected, the isochrone indicates the points from which the reference object can be reached within the same time.
Restrict search	Unlimited search If this option is selected, the route choice criterion is not limited. Cancel search when maximum value is reached If this option is selected, you can specify a maximum value for the route choice criterion selected. The shortest path search is canceled when this value is reached. This saves computing time. Maximum value Entry field for the maximum value of the route choice criterion. Note This field is only available if the Cancel search when maximum value is reached option is selected.
Generate POIs	If this option is selected, 2D surfaces are calculated and corresponding POIs are generated for each isochrone calculation for specified travel times. The POIs created in this way can be used in subsequent calculation operations, for example when intersecting with other surface objects or during shape export for further use in an external GIS. Click the button to make the desired settings. Network object type Select the network object type whose isochrone times are to be used. Propagation speed Enter the desired propagation speed. The propagation speed controls how much the attribute value of the network object increases with increasing distance. Maximum propagation radius Optionally enter a maximum propagation radius. The maximum propagation radius is the maximum limit up to which an attribute value may propagate from a network object. POI category Display of the POI category in which the POIs are to be generated. Click the button to open the window in which you can add, edit, and delete categories (Editing a POI category). If necessary, change the category in which the POIs are created. If necessary, delete existing POIs using the corresponding button. Travel times The table contains the set of travel times in minutes for which isochrone surfaces are to be calculated and saved. Use the symbol to insert further travel times. Enter the desired value > 0 in the new row. You can also edit or delete selected rows in the table. Copy classification of 2D display Clicking this button transfers the classification settings from the 2D display (Two-dimensional display of attribute values around point objects). Note The POIs generated in this way are provided with user-defined attributes with the values of the isochrone calculation.

5. Depending on the network object type selected, in the network click the desired node, main node or zone.

Tip: Alternatively, to select a network object, right-click in the network and search for the desired network object in the search window (Finding network objects in the network).

Note: If on the toolbar, the Click only active objects button is activated, you cannot use the mouse to select passive network objects (Marking only active network objects).

In the Graphics tools (Isochrones) window, in the Selected network objects section, a new row is displayed for the selected object.

Note: To edit the network object displayed, in the Selected network objects section, click the network object and in the search window, search for the desired network object (Finding network objects in the network).

6. If required, click further nodes, main nodes, or zones.

Notes: You can undo your selection by clicking a selected object again.

You can select network objects of different object types simultaneously. To achieve this, change the entry in the network object type drop-down list in the Graphics tools (Isochrones) window.

7. Click the Execute symbol .

The isochrones are displayed according to your settings.

Notes: In isochrone mode, you can use the functions from the Network editor window's toolbars without leaving the isochrone mode.

You can switch off the display by clicking the Reset button.