Environmental Engineering Reference
In-Depth Information
5
Note that the area devoted to streets gives a distorted view as density is not controlled for. So a city with
low density can have a low per cent of land allocated to streets, whilst a city of high density can have
a higher per cent of land allocated to streets. For example, the San Francisco peninsula has a population
density of 17,166 persons per sq mile and 26 per cent of land is devoted to streets; the corresponding
figures for Downtown Dallas are 4,339 and 13 per cent and the core of Shanghai 17,728 and 7 per cent.
In many rapidly growing cities, there are high densities and low per cent of land allocated to streets, thus
exacerbating the problems of movement.
6
Theory derives from Ancient Greek (
theoria
) meaning 'looking at, viewing, beholding', and refers to
contemplation or speculation, as opposed to action or 'practice' (
praxis
). In the social sciences, theory
is seen as illuminating the 'concrete processes of human life' (Giddens, 1984). For example, in transport,
theory would seek to understand the reasons behind travel, whilst transport practice seeks to move people
around more effectively. In transport planning, theory has been most developed in transport modelling,
often in mathematical terms, in attempting to more effectively model the real world. There are relatively
few attempts to understand why people actually travel, and how they might be encouraged to travel in
different ways.
7
Ontology: the philosophical study of the nature of 'being, existence, or reality', as well as the basic
categories of being and its relations to others. In the transport domain: what is the nature of travel, what
are its essential properties, and hence why do feel we need to travel? These types of questions should be
addressed before we plunge into the engineering of transport networks.
