Geography Reference
In-Depth Information
settlement pattern, the locations of consumer
services and transport linkages.
Such a consumer view requires planning to be
driven not by demand, as at present, but to be
'needs-based'. Questions of access to what, where,
and how often, should not be circumscribed by
existing travel patterns but based on an assessment
of people's needs. The concept of transport
need
is
a difficult one (Bradshaw 1974; Koutsopoulos
1980) and may be expressed by perceptual,
comparative or normative methods (see below).
Measured in terms of accessibility, a certain
proportion of needs will be satisfiable by the
facilities and transport in any area, but the residue
of
unfulfilled needs
can be taken to represent the
'problem'. It is vital to distinguish needs from
'demand'. As understood by economists, the
demand for transport is the amount actually
consumed; if this was equivalent to need then no
problem would exist. In rural areas, many travel
needs are frustrated because of the lack of suitable
transport services (
suppressed
or
latent
demand). The
whole point is that total demand exceeds transport
supply.
There is a similar impasse with studies of
mobility.
Mobility
is simply the ability to move
around, regardless of destination or purpose.
Potential mobility
is determined first by health and
fitness factors, and second by the availability of
transport, either private or public.
Actual mobility
refers to the amount of travel undertaken, usually
measured by traffic levels or trip rates (trips/
person/week). Results from questionnaire surveys
on travel behaviour therefore tell us more about
the successfully mobile sectors of society, and
much less about disadvantaged groups. Trips that
cannot be made are not recorded.
in the subject is by no means evenly spread around
the world. Far more work has been done in the
UK than in any other country, mainly between
1970 and 1985. This is probably because of the
tradition of public services, and great awareness of
the decline of public transport, which had
previously been abundant. For a general survey of
historic trends, transport policies and accessibility
applications see Moseley (1979) and Nutley (1992;
1998). In other countries, priorities or cultural
values may be different, data might not be
available, or the techniques might not be
transferable.
Simple methods
The simplest way of indicating accessibility is to
present a map depicting 'all areas beyond
x
km of
a major road' (or a railway, or a bus route). This
can be improved by calculating 'percentage of
population beyond
x
km of a transport route'. This
is obviously still of limited use. For example, only
about 5 per cent of the population of rural Britain
is beyond the reach of a bus or train service, which
might sound reasonable, but this does not say
whether the transport goes to the right places at
the right times and with sufficient frequency.
Density measures are sometimes seen, for example
'x
km of road per 100 sq km'. These are useful
only where there is a lack of further data, such as
in a historical situation or in the case of under-
developed regions (Box 35.1).
Network methods
Since the 1960s, network analysis has been used
to express the accessibility of places relative to
others in the same regional system. This involves
abstracting a network of roads or public transport
routes, converting it to matrix form and working
out the shortest paths between each node and
every other. Row totals in the matrix then
constitute the relative accessibility of each node;
these may be mapped as isarithmic surfaces. An
example is Lannoy and Oudheusden (1978), but
such techniques are now less popular. A common
extension is to weight nodal values by population,
TECHNIQUES AND CASE STUDIES
The rest of this chapter is devoted to a review of
the techniques developed by geographers to
evaluate rural accessibility and related concepts.
Policies, on the other hand, have shown less sign
of geographical influence. It should be pointed out
at this stage that the extent of geographical interest
