Defining the rail route inside the site

The railway track inside the site runs from the northern corner along the east side of the site to the unloading point 100 m to the north of the chlorine sphere.

Drawing the route on the GIS

You will define the route by drawing it as a single polyline on the GIS Input View, as follows:

1.Move to the GIS Input View, and use Zoom and Pan options in the General tab of the Ribbon Bar to arrange the view so that the site fills most of the display area.

2.Select the Route segments folder, then insert a segment.

3.Click at the northern corner of the site to place the first point on the route, then click to place each intermediate point, and finally double-click about 100 m to the north of the chlorine sphere as shown to stop drawing the segment.

A node named Route segment will be added to the tree. It will not be shown as greyed out, as it has automatically been added to the Model Playlist for the active Run Row.

4.Change the name of the segment node to Track inside site.

Completing the input data for the route segment

The input data for a route segment has several mandatory input fields, as shown.

You can define any number of Scenario groups under a given Route Model, and you must use the Scenario group dropdown list to select the group that you want to model at each failure location for this route segment. There is only one group for this Route Model, but you must still select it from the list in order to complete the input data.

The program will model the same set of hazardous events at regular intervals

along the segment, where the interval is set by the value for Spacing of events.

You should set the spacing to be less than the minimum effect distance for the group of hazardous events, since this will ensure that the effect zones from adjacent failure-locations overlap, giving the smooth distribution of risk along the route that would be observed in reality.

For this tutorial, you should set an initial value of 50 m. After you have run the consequence calculations and assessed the range of effect distances you can adjust this if appropriate. If you find that the spacing that you have chosen is too large, and is producing visible distortions in the risk contour results (e.g.

“bumps” in the contours every 50 m), then it may be necessary to reduce the spacing and rerun the calculations.