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BITRE | Working paper 74

For as long as there has been road congestion, there have been ways for dealing with

that congestion. These strategies can be loosely grouped into two categories: those

aimed at increasing supply and those aimed at reducing demand (or, to put it another

way, those that target the infrastructure and those that target the users). This chapter

reviews the primary strategies.

2.1 Increasing supply of road space

There are two basic ways of enhancing road space:

• physical expansion of capacity

• better utilisation of the available road space.

Physical expansion of road space

Crowded roads often trigger the expansion of road capacity, through the construction

of new roads, the addition of lanes or through utilising the hard shoulder during

peak-periods, as on some roads in England. Logically, if kilometres travelled increases

faster than the space available, congestion is likely to increase. Congestion in the US

has increased more where network expansion falls significantly behind growth in the

demand for road space.

However, the number of lane kilometres added does not tell the whole story. Poorly

selected expansion of road capacity may do little to relieve congestion. In contrast,

the astute expansion of the network can make a major contribution to traffic flow. An

internal or external bypass of a city can significantly relieve congestion. In Australia,

the expansion of the urban motorways in Sydney and Melbourne has provided

significantly faster travel options. In particular, the 2006 opening of Westlink M7, a

40-kilometre motorway through western Sydney provided a new route that avoided

up to 48 sets of traffic lights and reduced travel time on the north–south trip by up to

40 minutes. 3 Illustrated in Figure 2.1, the M7 provided the ‘missing link’ in Sydney’s

orbital road network.

Such strategic expansions in network capacity can make a major difference to

congestion. Thus, despite traffic volume growth of around 45 per cent over the past

15 years, the average peak hour speeds on the seven major routes to and from the

Sydney CBD have hardly changed (NSW RTA 2006, p. 27).

Significant gains in traffic flow have also been achieved with Melbourne’s 22-kilometre

CityLink motorway (see Figure 2.2), connecting three major urban freeways that

previously terminated at the edge of the highly congested CBD.

The story is echoed around the world. Britain’s first major toll road in modern times,

the M6 Toll, was built to relieve congestion on the M6. 4 Previously, the busiest section

of the nearby M6 Motorway was carrying up to 180 000 vehicles per day—more than

double its design capacity. The M6 Toll is reported to have reduced congestion

3. The M7 is also known as the Western Orbital.

4. The M6 Toll was previously known as the Birmingham Northern Relief Road.

8

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