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Page 1 Cobain Schofield
Retail Catchment Analysis in the West Midlands
Basic Buffer Catchment Analysis
Figure 1 shows a basic buffer map with primary and secondary catchment areas centred on each
retail centre within the West Midlands. The buffers are based on simple Euclidean distances of
1,500m for the primary catchments and 3,000m for the secondary catchments – these distances
are based on walking times of 15 and 30 minutes respectively with an average walking speed of
3.1mph (Aspelin, 2005). This method assumes uniformity in all directions and a constant walking
speed without obstacles. It also assumes that each retail centre has an identical catchment, which
is not the case in reality. Suggested catchment areas were not used owing to overcrowding on the
map and a loss of visual clarity.
Figure 1 – Basic primary and secondary catchment areas for each retail centre in the West
Midlands study area.
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Birmingham
Wolverhampton
Merry Hill Centre
Bilston
Tamworth
Harborne
Aldridge
Halesowen
ErdingtonPerry Barr
Northfield
Bromsgrove
Stourbridge
Kings Heath
Shirley, Solihull
Ventura Road Retail Park, Bitterscote
Solihull
Redditch
Coventry
West Bromwich
Sutton Coldfield
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( 1 - Major Retail Location
!( 2
!( 3
!( 4 - Minor Retail Location
Primary Catchment
Secondary Catchment
Birmingham LSOAs
Page 2 Cobain Schofield
Ranked Buffer Catchment Analysis
Figure 2 acknowledges that each different type of retail centre will attract people from different
areas for a range of different reasons including store type and diversity, as discussed by Steiner
(1998). However, these ranked catchments still assume identical catchment properties for each
rank category.
Figure 2 – Basic primary and secondary catchments ranked according to Table 1
Table 1 – Catchment radiuses for each retail centre rank, calculated according to Dramowicz (n.d)
Primary Catchment Radius (m) Secondary Catchment Radius (m)
Rank 1 8000 3600
Rank 2 5000 2250
Rank 3 3000 1350
Rank 4 1500 675
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Birmingham
Wolverhampton
Merry Hill Centre
Bilston
Tamworth
Harborne
Aldridge
Halesowen
ErdingtonPerry Barr
Northfield
Bromsgrove
Stourbridge
Kings Heath
Shirley, Solihull
Ventura Road Retail Park, Bitterscote
Solihull
Redditch
Coventry
West Bromwich
Sutton Coldfield
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( 1 - Major Retail Location
!( 2
!( 3
!( 4 - Minor Retail Location
Primary Catchment (Ranked)
Secondary Catchment (Ranked)
Birmingham LSOAs
Page 3 Cobain Schofield
Applying the Huff Model to Establish Retail Catchments
The Huff Model of Retail Gravitation (1964) was used to estimate catchments around each retail
centre based on the LSOA map of Birmingham. Some parameters were supplied, although some
were edited according to Huff (2003). The tertiary parameter value was altered from 0.2 to 0.25 to
maintain a 50% decrease in value from primary to secondary to tertiary. This increased the tertiary
catchment area from 16.7km2 to 18.3km2. This shows the tertiary catchment extending throughout
the map rather than being solely based around the north western quadrant.
This model does not rely on arbitrary Euclidean distances, but it does not differentiate between
each town centre; it is not possible to differentiate and identify all catchments, particularly in the
more densely populated areas around Birmingham.
Figure 3 – Basic Huff Model showing primary, secondary and tertiary catchments across the study
area.
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Birmingham
Wolverhampton
Merry Hill Centre
Bilston
Tamworth
Harborne
Aldridge
Halesowen
ErdingtonPerry Barr
Northfield
Bromsgrove
Stourbridge
Kings Heath
Shirley, Solihull
Ventura Road Retail Park, Bitterscote
Solihull
Redditch
Coventry
West Bromwich
Sutton Coldfield
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( 1 - Major Retail Location
!( 2
!( 3
!( 4 - Minor Retail Location
Huff Model Catchments
Tertiary Catchment
Secondary Catchment
Primary Catchment
Page 4 Cobain Schofield
Multiple Attribute Huff Model
Figure 4 shows the same data as Figure 3 but with each catchment coloured differently to help
distinguish each retail centre. The lightest colours around each retail centre show tertiary
catchments, while the darker colours are primary catchments. The predominant Khaki colour
covering much of the map represents Birmingham’s secondary catchment; however this is
questionable given the extent of the expanse.
Figure 4 – Huff Model showing individual catchments around each retail centre
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Birmingham
Wolverhampton
Merry Hill Centre
Bilston
Tamworth
Harborne
Aldridge
Halesowen
ErdingtonPerry Barr
Northfield
Bromsgrove
Stourbridge
Kings Heath
Shirley, Solihull
Ventura Road Retail Park, Bitterscote
Solihull
Redditch
Coventry
West Bromwich
Sutton Coldfield
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( 1 - Major Retail Location
!( 2
!( 3
!( 4 - Minor Retail Location
Huff Model Catchments
Tertiary Catchment (Lightest)
Secondary Catchment
Primary Catchment (Darkest)
Page 5 Cobain Schofield
Combined Ranked Buffer and Huff Catchments
Figure 5 shows the disparity between the catchment areas calculated using the Huff Model and
those generated through the ranked buffer methods in Figure 2. This is because the Huff Model
accounts for factors which differ between each retail centre.
Figure 5 – Combined catchment map comparing the extent of ranked buffer zones from Figure 2
with catchments generated by the Huff Model in Figure 3
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Birmingham
Wolverhampton
Merry Hill Centre
Bilston
Tamworth
Harborne
Aldridge
Halesowen
ErdingtonPerry Barr
Northfield
Bromsgrove
Stourbridge
Kings Heath
Shirley, Solihull
Ventura Road Retail Park, Bitterscote
Solihull
Redditch
Coventry
West Bromwich
Sutton Coldfield
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( 1 - Major Retail Location
!( 2
!( 3
!( 4 - Minor Retail Location
Secondary Catchment (Ranked)
Huff Model Catchments
Tertiary Catchment (Lightest)
Secondary Catchment
Primary Catchment (Darkest)
Page 6 Cobain Schofield
Generating Catchments based on the Road Network
Road Network data for the West Midlands was obtained from Edina and a basic road network was
established. Catchments were generated based on the distance from each retail centre by road
only. As mentioned in ESRI’s guide to using OS ITN (2007), the road network data is “limited by
the lack of speed limit information on roads and inability to differentiate between urban and
rural areas”. The dataset is also absent of road direction data, traffic control systems and public
transport networks.
There are broken links in road junctions on the dataset which cause errors in the processing, such
as the ~25% empty area north east of Wolverhampton, as detailed in Figure 7 on Page 7. These
are apparently caused by obstacles such as railway lines (Figure 8).
Figure 6 – Rank 1 retail centres with catchments derived from the road network.
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Birmingham
Wolverhampton
Merry Hill Centre
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( Rank 1 Retail Centre
Rank 1 Roads
Rank 1 Catchments
Birmingham LSOAs
Page 7 Cobain Schofield
Figure 7 – Broken road links 0.25 miles outside Wolverhampton hamper the generation of road
network catchments
Figure 8 – Railway lines appear to be causing broken links in the road network in Figure 7
!(Wolverhampton
±
0 0.25 0.5 0.75 10.125Miles
Legend
Retail Centre Hierarchy Ranks
Rank
!(1 - Major Retail Location
Birmingham LSOAs
Rank 1 Roads
Rank 1 Catchments
Credit: Google Maps
A on Figure 7
B on Figure 7
A
B
Page 8 Cobain Schofield
Figure 9 - Rank 2 retail centres with catchments derived from the road network.
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Walsall
Solihull
Redditch
Coventry
West Bromwich
Sutton Coldfield
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( Rank 2 Retail Centre
Rank 2 Roads
Rank 2 Catchments
Birmingham LSOAs
Page 9 Cobain Schofield
Figure 10 – Combined Road Network catchments for retail centres ranked 1 to 4
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Birmingham
Wolverhampton
Merry Hill Centre
Bilston
Tamworth
Harborne
Aldridge
Halesowen
ErdingtonPerry Barr
Northfield
Bromsgrove
Stourbridge
Kings Heath
Shirley, Solihull
Ventura Road Retail Park, Bitterscote
Solihull
Redditch
Coventry
West Bromwich
Sutton Coldfield
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( 1 - Major Retail Location
!( 2
!( 3
!( 4 - Minor Retail Location
Birmingham LSOAs
Rank 1 Roads
Rank 1 Catchments
Rank 2 Roads
Rank 2 Catchments
Rank 3 Roads
Rank 3 Catchments
Rank 4 Roads
Rank 4 Catchments
Page 10 Cobain Schofield
Figure 11 shows that the higher ranked retail centres have road network catchments which extend
as far as, or almost as far as the secondary buffer catchments when the same distances are used.
The smaller centres may not extend so far, as road networks are not as dense nor direct as those
in the larger towns and cities Therefore, one must travel further along roads before reaching the
edge of the buffer catchment.
Figure 11 - Combined catchment map comparing the extent of ranked buffer zones from Figure 2
with catchments generated by the road network.
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Birmingham
Wolverhampton
Merry Hill Centre
Bilston
Tamworth
Harborne
Aldridge
Halesowen
ErdingtonPerry Barr
Northfield
Bromsgrove
Stourbridge
Kings Heath
Shirley, Solihull
Ventura Road Retail Park, Bitterscote
Solihull
Redditch
Coventry
West Bromwich
Sutton Coldfield
±
0 3 6 9 121.5Miles
Legend
Retail Centre Hierarchy Ranks
!( 1 - Major Retail Location
!( 2
!( 3
!( 4 - Minor Retail Location
Birmingham LSOAs
Secondary Catchment (Ranked)
Rank 1 Roads
Rank 1 Catchments
Rank 2 Roads
Rank 2 Catchments
Rank 3 Roads
Rank 3 Catchments
Rank 4 Roads
Rank 4 Catchments
Page 11 Cobain Schofield
Data Sources
All maps are based on Edina Census Geography shape files.
1 Birmingham Shape Files (mapping): Edina “Census Geography” http://census.edina.ac.uk
2 OS MasterMap ITN Layer (mapping): Edina Digimap “OS MasterMap ITN” http://digimap.edina.ac.uk
Colouration of all maps is based on Cynthia et al (2003) so as not to discriminate against those
with vision impediments or colour blindness.
References
Aspelin, K. (2005) “Establishing Pedestrian Walking Speeds”. Portland State University. Available
at: http://www.westernite.org/datacollectionfund2005/psu_ped_summary.pdf; Accessed: 24th
March 2015
Cynthia, A. (2003) “A transition in Improving Maps: The ColorBrewer Example” in U.S Report to
the International Cartographic Association, special issue of Cartography and Geographic
Information Science 30(2);155-158.
Cynthia, A. and Mark, A. (2003) “ColorBrewer.org: An Online Tool for Selecting Color Schemes
for Maps”. The Cartographic Journal 40(1):27-37.
Dramowicz, E. (n.d) “Retail Trade Analysis Using the Huff Model”. Directions Magazine. No
published date available. Available online at: http://www.directionsmag.com/entry/retail-trade-area-
analysis-using-the-huff-model/123411; Last accessed: 24th March 2015
ESRI (2007) “Using OS MasterMap Intergrated Transport Network (ITN) Layer with ArcGIS: An
ESRI (UK) White Paper”. Published by ESRI (UK) Ltd, Buckinghamshire, UK. Version 2.0.
Google Maps – Map of Wolverhampton utilised in Figure 8. Available online at:
http://goo.gl/d6hNpG; Last accessed: 27th March 2015
Huff, D. (1964) “Defining and Estimating a Trading Area”. Journal of Marketing, American
Marketing Association. Volume 28 (July 1964), pp. 34-38
Huff, D. (2003) “Parameter Estimation in the Huff Model”. ArcUser, October-December 2003
Edition, 34-36
Steiner, R. (1998) “Traditional Shopping Centres”. ACCESS Magazine. University of California
Transportation Centre, 4th January 1998.