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GENERIC STEP-BY-STEP APPROACH STEP THREE

Table 3: Speeds used in the accessibility modeling for different types of roads and modes of transport

ACTIVITY 5 – DETERMINE CURRENT LEVELS OF ACCESSIBILITY

OF SERVICE POINTS

In order to determine the current accessibility of service points you need to conduct an unconstrained
catchment area analysis using the GIS accessibility modelling software. The unconstrained analysis
means that no geographic access standards, including travel distance/time constraints and maximum/
minimum population parameters for service points, are taken into consideration in developing current
accessibility statistics.

You can use the accessibility maps and statistics generated in unconstrained analysis to identify areas
that are currently underprovided, sufficiently provided and/or overprovided with service points. The
assumption is that people will travel to their closest service points.

You will also be able to develop service area catchment profiles that include the following:

 The number of people each service point currently has to deal with in its unique catchment area.

 The average distance or time that people in the catchment area currently travel to the closest service
point.

 The worst case travel distance or time for people to travel to service points.

 The travel distances or times for different percentages, for instance 95% or 99%, of the target
population travel to reach different types of service points.

By examining the accessibility statistics it is possible to identify districts where access to service points
may have to be improved. You can do this by comparing the population demand and travel distances to
the various service points with each other.
Once you have prepared the spatial data for your study (see Activity 4) you need to import it into your GIS
accessibility modelling software in order to generate the accessibility statistics for the geographic study
area. Go ahead with the analysis as follows:

 Use the software to develop travel distance tables.

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