Population, land use and travel - Transport Policy and Planning in Great Britain - page 23

overall increase in population was the result of natural increase more than offsetting
its effects. Today the situation is quite different with net in-migration accounting for
two-thirds of the population increase.
More important for planning purposes are local variations in the rates of population
change, principally the product of migration amongst different age groups. A key
feature of the last fifty years has been the phenomenon of 'counter-urbanisation' - a
general shift of population from conurbations and larger cities to freestanding towns
and rural areas (Breheny 1995). When analysed by local authority area most large
towns and cities continue to show population losses for this reason. Exceptions are
Cardiff, Leicester, Leeds/Wakefield and Aberdeen plus Edinburgh and Greater London
which have reversed the trend altogether.
In many parts of the country however this counter-urbanisation process takes
the form of a spreading out of cities from within their traditional boundaries into
dormitory areas beyond. Rather than an overall loss of population the change is
therefore better represented as a local redistribution within a wider area. If analysis
is conducted using 'functional regions' (based on Travel to Work Areas rather than
individual local authorities) the pattern becomes clearer (Champion and Dorling
1994). There are some places (notably Glasgow, Tyne and Wear and much of
Merseyside and Greater Manchester) where major losses from the cores of cities
have not been offset by gains in surrounding areas, resulting in overall decline. On
the other hand there are places such as the West Midlands and Bristol where losses
within the core have been countered by significant growth in at least some of the
surrounding districts.
There is also a large area of south-eastern Britain where almost no part has
experienced significant population loss and in many places there have been substantial
gains. Over the last 15 years or so this has included Greater London itself. Intriguingly
the boundary of this area almost exactly follows the line of Fosse Way - the Roman
road running north-east/south-west from Lincoln via Leicester and Bath to Exeter. It
is to this south-eastern half of the country that the bulk of migration, from both within
and outside Britain, is taking place. The only other urbanised region characterised by
significant growth in both the core city and its environs is Edinburgh, although on a
much smaller scale.
Shifts in the distribution of the population gradually alter local densities. Population
density is of fundamental importance to transport as areas with higher densities have
more opportunities closer at hand and thus tend to offer better accessibility and generate
shorter trips. They also imply more intensive travel demand within a given area. This
suggests greater potential for public transport on the one hand (because it benefits
from economies of scale) and greater probability of traffic congestion on the other.
Conversely low density areas tend to be associated with poorer accessibility, longer
trips, limited scope for public transport and greater opportunity for the unconstrained
use of the private car. As discussed later (2.6) these density effects are compounded -
for better or worse - by patterns of land use and urban form.
The overall pattern of settlement - i.e. the spatial distribution of the population -
has been shaped by mobility constraints in the era before motorisation and by town
planning policy since. The result in most areas is a quite a sharp distinction between
urban (predominantly built-up) and non-urban (predominantly rural) areas. Most of
urbanised Britain has overall densities of between 20 and 40 persons per hectare (by
local authority area). Only Inner London is more densely occupied than this. Small
towns have densities at the lower end of this range but since a higher proportion of