PDF: 1832 KB - Bureau of Infrastructure, Transport and Regional ...


PDF: 1832 KB - Bureau of Infrastructure, Transport and Regional ...

Chapter 2 | Prevailing strategies to manage congestion

Figure 2.3 US road capacity growth and mobility level


53 areas


Demand grew more than 30 per cent

faster than supply

Congestion Growth Index





28 areas

Demand grew 10 to 30 per cent

faster than supply

4 areas

Demand grew 10 per cent

faster than supply


1982 1989 1996 2003

Source: Schrank and Lomax (2005, p. 55).

As land take increases, so does the cost of expanding capacity. For Singapore, an

island with a land area of 700 square kilometres, it has been estimated that the cost of

dealing with traffic growth by expanding the road network (instead of implementing

their pioneering congestion charging scheme) would have cost around $S1.5 billion

(Menon (2003, p. 124), quoting a World Bank study from 1984).

In theory, capacity expansion is justified when the marginal cost of congestion

exceeds the marginal cost of expansion (see page 58). There will always be network

expansion options that do not absorb land. These include deep tunnelling, ‘cut and

cover’ tunnelling and double stacking of roads. However, these options come at a

significant financial cost and, often, unpalatable environmental costs.

Nonetheless, despite apparently crippling levels of road congestion, it is not unusual

for the financial cost of expansion to far outweigh the congestion costs, particularly

in built-up areas. We note that the more built-up the area, the greater will be the

community resistance and, thus, the lower the political acceptability.

A good illustration of this is the 1960s London Ringways plan advanced by the

Greater London Council: the plan involved building a series of motorways in and

around London to accommodate the expected growth in traffic. Public opposition

was widespread, but particularly so for the route south of the Thames, Ringway 2,

otherwise known as the South Circular. The local newspaper reported that ‘2,189

homes will be demolished and schools, churches, playing fields, sports grounds,

swimming baths, public halls, allotments will be taken or affected to some degree’

(C. Marshall undated). As noted on an unofficial British roads website: ‘… only way

was to pick a line and follow it—to mirror railway lines and to buy up golf courses,

and for the rest of the route, to draw a line and bulldoze every building that stood in

the way’ (CBRD undated).