On the surface - The Visualization of Spatial Social Structure - page 219

Box 7.3 Travel time surface
In travel-time space, internal airlines would hang like the lines for cable
cars between the peaks representing airports. The surface would undulate
smoothly in response to the pressure of traffic on the roads and the general
quality of the infrastructure. A main line railway would form a ridge along
which settlements cluster in the search for access to work in the city, coupled
with the desire to sleep away from it. Occasionally, an international airport
may create a hole in this fabric, down
which travellers can speed to distant
locations.
The travel-time surface would show
us the economic shape of the country.
It may also tell us how some decisions
were made as to where to locate factories
and why many people live where they
do. In some places the surface would
be monotonous; elsewhere it could be a
tangled mess. It would change with the
hours and the years, revealing yet another
shape to the country.
of minor roads, or more appropriately tunnels, as they could only be accessed
at specific intersections. The ease of access, where it occurred, would need to
be made clear. Congested city centres can be cut into by great trunk roads and
railways. If internal airlines were included for passenger transport, they might
appear as a tightrope connecting the city mountain tops together (Box 7.3).
Euclidean space need not be the two-dimensional basis for such projections
upwards. Using Euclidean space in this way only tells of the difference between
physical distance and travel time. If a population cartogram were used as the
base from which points were projected, so that the distance between points was
proportional to the time travelled, the cities would flatten and the land in between
rise up. The picture would not be nearly as mountainous as before, as distance
in population space is much closer to travel time. The highways and motorways
would form a river system into which all other roads appeared to flow, the more
minor ones being the headwaters at the highest points on the surface formed.
What is more, upon a population-cartogram-travel-time-surface it would be
possible to drape, and see information about, the population between which the
roads flow. A multicoloured mosaic of places could be seen rising up in the areas
of inaccessibility, spread evenly over the well-connected plains, where the roads
were many and the vehicles on them were relatively few. Such an image would
help us to understand that the industrial structure of Britain was created using
different means of spatial accessibility (coast, river, canal, rail, then road). Such