Calculating service areas

A service area is a region that includes all streets that can be accessed within an impedance defined by time or distance from a point in a network that you choose on the map. For example, a 10-minute service area of a fire station would include all those streets that can be reached within 10 minutes from the fire station. Multiple service areas can also be overlapped. Perhaps you want to define a service area for a community center by seeing how many residences are within 1 km, 2 km, or 3 km radius of the community center.

 

NOTE:

Your map administrator must set up service areas and available options for their definition. Not all the options described here may be available.

1.	If the Map tools pane is not expanded, in the map viewer, click the Map Tools button.

2.	On the Map Tools pane, click the More Tools button and then click Network Analysis. The Network Analysis dialog box appears.

 

Figure 309 

Selecting the Network Analyst tool

3.	In Analysis Type, select the service-area analysis type. If only one service-area analysis type is available, it is shown here and you need not select it. However, if more than one is available, you have the option of selecting the type of analysis here.

4.	You have the option of selecting a map feature or drawing a markup shape on the map that will serve as the focal point for the calculation of the service area. This focal point is also called a facility.

•	For example, if you wanted to compute a service area for a school, you would select that school as the facility.

a.

To select a feature on the map as the focal point of you service area, in Facilities, click the Start Selections button and using the Selection tools, select the one or more map features you want to use a the center of the service area. See Selecting a map feature to use as a focal point for the service area.

b.	To draw a markup shape on the map to use that as the focal point for the service area, in Facilities, click the Draw Markup button and use the Markup tools to draw a shape on the map.

Selecting a map feature to use as a focal point for the service area

•	Click one of the selection tools. Position the cursor close to the one or more map features you want to select. Hold with the mouse, drag and release the mouse to draw a selection shape.

•	Any map features that are within or that intersect the selection shape you drew are labeled on the map, and their related attribute data are displayed on the Results window in the lower portion of the map viewer.

 

Figure 310 

Selecting a map feature for which a service area will be calculated

 

Drawing a map feature to use as a focal point for the service area

5.	On the Network Analysis window, review the options described below and fill them in as necessary:

 

Table 35 

Network Analysis settings for service areas described

Setting	Description
Facilities	If you selected a map feature to be the focal point of the service area, its layer is shown here. If you drew a markup shape to be the focal point of the service area, Markup is shown here. A facility is the focal point around which a service area is calculated.
Impedance	Select the type of constraint to travel to the facility (map feature you selected at the beginning of the procedure). Your map administrator configures the options that are available, which may vary. Length • Set Impedance to this option to make distance from or to the facility the constraint to travel when calculating the service area. For example, an impedance of 10 meters would result in a buffer zone surrounding the facility including all areas accessible within 10 meters. Time • Set Impedance to this option to make travel time from or to the facility the constraint to travel when calculating the service area. For example, an impedance of 10 minutes would result in a buffer zone surrounding the facility including all areas within a drive time of 10 minutes.
Breaks	Specify one or more breaks to create multiple concentric service areas for the one or more facilities. You must specify numeric values separated by commas and then select a unit of measure. For example, if you selected a school as the facility for which you wanted to calculate a service area, and set Impedance to Time, and specified 10, 15, 30 in Breaks and selected Minutes. Three concentric service areas would be plotted on the map, showing three concentric service areas radiating from the school from where travel time to the school is 10, 15 or 30 minutes.
Restriction	Select the restrictions you want to be observed when calculating the service area for the facility. These are determined by your map administrator. A common restriction is the height or weight limits that prevent certain vehicles from traveling on some roads or bridges.
Travel Direction	From Facility • Select this option to have a service area created by taking into account the constraint to travel with the facility as the staring point. To Facility • Select this option to have a service area created by taking into account the constraint to travel with the facility as the destination. The correct travel direction depends on the nature of your service area analysis. The service area for a delivery service, for example, should be created in the travel direction that goes away from the facility since deliveries are carried out from the facility to the customer. Alternatively, a health center should choose the opposite direction since the urgent part of the trip for an incoming patient is getting to the destination.
Output Geometry	Polygon • A shape is produced as the output map feature representing the service area. Polyline • Resultant service area represented as network edges that can be reached within the given impedance. Both • A shape and its boundary are produced as the output map feature depicting the service area.
Polygon Overlap Option	Overlap • Default setting. Creates individual service area shapes for each facility (each of the map features you selected or markup shapes that you drew at the beginning of the procedure). Service area shapes can overlap. No Overlap • Create individual service area shapes for each facility (each of the map features (each of the map features you selected or markup shapes that you drew at the beginning of the procedure). Service area shapes do not overlap. Merge by Break Value • This option merges the service area shapes that have the same break value, which you specify in Breaks. Breaks are the time or distance intervals used to create concentric service areas around the map feature specified as the facility.
Simplified Polygon Geometry	By default this setting is enabled. Simplified service area shapes are generated quickly and are fairly accurate, except in the fringes. If this option is not enabled, service area shapes are more detailed and may take longer to generate.

 

Figure 311 

Generating service areas

6.	Click Solve.

•	The map refreshes and displays the service areas around the facilities that were selected.

 

Figure 312 

Service area analysis showing 3 breaks