Network Operations arrow 2 Delivery arrow 2.3 Traffic Control
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2.3 Traffic Control Print

Increased economic activity stimulates transport demand for both individuals, goods and freight. The policy challenge is to determine whether to intervene with traffic control measures and how best to achieve the desired results. Local policy objectives vary from achieving the maximum unimpeded traffic flow without compromise, to one of severe traffic calming with priority to pedestrians, cyclists, animal transport and other classes of slow-moving traffic.

However intervention is more widely used to help achieve policy objectives.

Traffic management and traffic control can better distribute traffic across the network and helps balance demand. They can be used to prevent or to recover a poor traffic situation and to correct imbalances between competing priorities.

Preventative action

This aims to adjust travel demand. It may include warning drivers of anticipated problems so that they may change their travel times, choose different routes or abandon their trip. This requires:

  • A capacity to predict traffic disturbances (whether random, foreseeable or recurrent);
  • The study of advice or alternative routes, that can be used in the event of difficulties; and
  • Dissemination of preventive information to the users.

Remedial or corrective action

This is designed to limit the extent or impact of disturbances that occur regularly on major roads, through measures to limit access and divert traffic onto less congested routes. It requires:

  • Traffic management plans to be drawn up in conjunction with stakeholders  initiating measures to be implemented by the services concerned
  • The use of a permanent or ad hoc detection and monitoring system on traffic flow conditions: data collection, centralisation and processing with a view to diagnosing the situation and how it may develop, and initiating traffic management measures,
  • The implementation of operational action teams for guidance marking and closure of access in the absence of automatic systems, or when field monitoring is required;
  • Real-time road user information systems on disturbances, instructions or recommended routes, and
  • The activation of specific equipment for network information/management, such as information systems using variable message signs.

Demand management

Demand management covers all the operation measures that aim to limit activity on the network.  This is based on the mobility policy which may include improving traffic distribution through time or encouraging modal transfer. Among other tools, variable tolling is one of the means of adjusting demand

Enforcement

New technologies allow the use of automatic systems for enforcement, providing improved consistency in the detection of traffic violations. In addition, road network efficiency is improved and road surface damage is limited through increased compliance of traffic to mandatory regulations. Implementing automatic enforcement systems requires close co-operation with the Police and Justice department in order that the system in place complies perfectly with the legal system.

Active Traffic Management

Active Traffic Management is an approach that is being adopted, mostly in Europe, for heavily trafficked and congested expressways and motorways. It aims to smooth traffic flow and maintain or improve throughput by regulating speeds and through better utilisation of the available carriageways. It requires an integrated operation across all the different agencies directly involved, to improve the level of service offered to the road user. The agencies work together to develop the necessary operational procedures. The following methods are in use:

  • Active monitoring of the network to determine current and forecast traffic conditions, with heavy instrumentation, TV surveillance and comprehensive data collection.
  • Traffic management and control which is adapted to traffic conditions in real-time, both automatically and through operator interventions at the Traffic Control Centre.
  • Variable speed and lane control using overhead VMS signs and lane indicators
  • Mandatory variable speed limits imposed based on current flow conditions
  • Speed enforcement tied to variable speed signs and speed enforcement cameras,
  • Hard shoulder running at peak times to gain an additional lane of traffic
  • Incident detection and rapid-response rescue services
  • Driver information through VMS signage such as point-to-point journey times, traveller Information, highway advisory radio, and other traffic information
  • Other regimes such as, access control (ramp metering primarily), and dynamic lane use, such as High-Occupancy Toll (HOT) lanes.

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Chapter 4 of Road Network Operations Handbook “ITS Solutions”