All vehicle mileage (millions1993
1994

Measured growth in traffic (vehicle mileage) on the Isle of Wight, traffic growth projections made in
Newportjunction plan documents, and population change over time

 
 

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.o


.-

.o0'1 
0'1 

Actual

1998

1999
2000
2002
2003

2001

- 2008 model

2004

 

.
5'

Population growth
figures/projections
(National Statistics)

 

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.-
.-
.-
nu


.10'

 

 

2005
2006
2007
2008
2009
2010
2011

- 2018 model

nu"

2012

2013

2014

Population growth

 

 

 

 

 

 

 

 

 

 

.o
.-
.-

.-
..
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Actual vehicle mileage
calculated from counts

 

 

   

2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026

Trend vehicle mileage

Projected growth to 2020
I calculated from growth figures
I in Newport Traffic Model 2008
I
I Projected growth to 2034 calculated I
I from growth figures used for I
I current St Mary's Junction plan
I I
I
I
I
Gap between projected I
figures and actual 
measured traffic data 
Trend in population
growth closely matches
trend in traffic growth

 

 

 



Trend population

 
 
  
  

2034

185000

175000

165000

155000

145000

135000

125000

Population

What does the graph tell us?
1. The Newport traffic model of 2008 grossly overestimated growth in traffic levels.
2. The updated traffic model being used to support the large increase in capacity at the St Mary’s junction predicts traffic growth that is substantially
in excess of the increase one would expect from projected population growth.
3. The best measure for predicting future road capacity judging by data stretching back to 1993 is population growth forecasts. These currently stand
at 6.5% whereas the Council’s traffic growth forecasts stand at 22%.
Conclusion
This analysis appears to call into question the need for such a large increase in road capacity at the junction. We are not suggesting that no increase
in capacity is required going forward, but that the current scheme should be reviewed and that designs should be commensurate with realistic
projections based on forecast population growth, including detailed analysis of traffic that would be generated by any new development at Camp
Hill. Based on the information currently in the public domain this does not appear to have been done.

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