13. Traffic Management
13.1 Introduction
Traffic management can be thought of as the application
of a defined traffic control policy to an area or an extended length of road,
with the aim of achieving a specified set of community objectives. This means
that traffic management is distinguishable from a traffic control action
which applies to a particular intersection or trouble spot.
The types of objectives which may be required for
a particular traffic management scheme include:
- improvement of traffic conditions e.g. reduction
of congestion;
- improvement of physical environment e.g. reduction
in noise pollution;
- improvement of access e.g. to commercial areas;
- improvement of safety e.g. slowing of vehicles
to improve pedestrian or child safety; and
- reduction of parking problems.
In some cases a traffic management scheme will be proposed
in response to a particular problem or set of problems, and the measures
to be used will be fairly obvious. In other cases the nature of the problem/s
may be more complex and a range of alternative traffic management schemes
must be devised and assessed.
Implementation of a traffic management scheme will
usually mean an alteration in traffic flow patterns. This in turn will mean
that some roads, or sections of road, will carry heavier volumes than previously,
while other sections will carry lesser volumes. The community will therefore
probably perceive that some members of the community are advantaged, while
others are disadvantaged with the introduction of the scheme. Trade-offs
may therefore have to be made between different benefits and disbenefits.
This trade-off often occurs within a trial implementation of the scheme.
13.2 Major Urban Road Networks
An early step in the development of most urban traffic
management schemes is to define a desirable functional hierarchy for the road
network i.e. to define roads as arterials, distributors, collectors and local
streets. The management scheme should then produce traffic patterns which
are in accordance with the defined hierarchy system.
Traffic management schemes will seek to make travel
on the major road system (arterials and sub-arterials) as attractive as possible
so as to encourage their use. Measures to achieve this may include the following:
- Parking Bans. Parking bans, including the introduction
of clearways during peak hours, provide additional traffic lanes without the
need for construction work. Such bans may of course provide a disbenefit to
adjacent landholders.
- Access Control and Reduction. The performance
of arterial roads is greatly improved if the arterial traffic has absolute
priority at intersections with minor streets. This can be achieved by the
use of Stop or Give Way signs. However, even if this absolute priority exists
significant interference may still occur, and consideration may be given
to limiting the number of intersections at which access to the arterial is
possible.
- Intersection Improvements. The critical points
on most arterial roads are the intersections. Hence there is potential for
intersection improvements to greatly influence the performance of the road.
- Coordination of Traffic Signals. Coordination
of traffic signals along an arterial road or throughout a road network can
have the effect of increasing the overall capacity of the network without
reconstruction of the individual intersections.
- Designation of Heavy Vehicle Routes The removal
of heavy vehicles with large dimensions and slow acceleration characteristics
to particular routes may allow the rest of the network to perform more efficiently.
13.3 Local Areas
The preparation of traffic management schemes for local
areas must be undertaken in the context of overall traffic management. Actions
taken on arterial roads will have significant impact on local roads and vice
versa. A local traffic area is an area bounded by arterial roads in which
through traffic is of limited importance, and can therefore be justifiably
restrained.
Modern subdivision design will usually attempt to
‘design in’ Local Traffic Areas and so encourage through traffic to use the
arterial road system. Older established areas may be able to encourage the
development of local traffic areas by the following types of treatments on
local streets:
- Reduction of intersection conflicts by the use
of Stop or Give Way signs.
- Reduction of statutory speeds.
- Reduction of local street connectivity by full
or partial intersection closure.
- Reduction of local street connectivity by partial
prevention of access from major roads.
- Discouragement of through traffic by reducing
width of intersection openings from major roads.
- Reduction of speeds by changes of road format.
- Discouragement of through traffic by change
of nature of street entrance.
- Reduction of intersection speeds by use of roundabouts.
- Reduction of speeds by physical speed control
devices e.g. bumps, humps, dips, rumble strips, etc.
- Prohibition of large vehicles.
13.4 Rural Roads
The objectives of traffic management for rural roads
can be broadly classified as:
- capacity (e.g. increasing capacity at slow points
by the use of auxiliary lanes);
- safety (e.g. reinforcing a driver's perception
of safety by the use of consistent signing of hazards); and
- quality-of-service (e.g. providing motorists
with sufficient rest areas).
Page last modified 25 June 2002.