Road traffic management
Traffic data is a vital element both in real time to operate the road network (notably by supplying data for traffic management support systems) and in non-real-time to inform public policy and produce relevant statistics. For example, traffic data is used to:
draw up management, operational and maintenance policies for the national road network
monitor transport policy, notably changes in road traffic and its impact on the environment
optimise the use of existing infrastructure to meet the objectives set out in the Grenelle de l’’Environnement (the French round table on the environment) and the National Transport Infrastructure Plan
draw up and monitor the impacts of public road safety policies
produce short, medium (the Bison Futé traffic information service in France) and long-term traffic forecasts and supply traffic forecast models for the ex-ante assessment of infrastructure policy etc.
The users of this data are diverse:
within the ministry: Central government directorates, DIR (Interdepartmental Road Services), Regional Services for the Environment, Area Planning and Housing, members of the Scientific and Technical Network etc.
Road managers excluding the State: Departmental Councils, Urban Communities etc.
Engineering companies etc.
The Data Collection System
Traffic data is collated by the ministry’s Traffic Information System (TIS) under which the DIR collect data which is entered into local databases. These local databases are then merged to form the national traffic database.
The data collection system uses the Siredo stations installed across the national road network.
With the emergence of new sensors and measuring equipment, the current challenge is to improve the data collection system both in terms of the quantity and quality of the traffic measurements produced.
(see the article on sensors opposite)
Data collected and traffic indicators
The main data collected are: Traffic flow rate, occupancy rate, average vehicle speed.
Other more precise data can also be collected, depending on the type of equipment fitted: For example, flow distribution by distance, speed, silhouette and weight.
This traffic data is then used to draw up traffic indicators, notably Annual Average Daily Traffic Flow, Monthly Average Daily Traffic Flow and the percentage of Heavy Goods Vehicles (%HGV) The main application and use of these indicators is to calculate the National Traffic Index (see Traffic index for the national road network), information on border traffic, current transport statistics (e.g. National Transport Audit Office whose latest report is available at:
http://temis.documentation.equipeme..., and various publications including the annual traffic map, etc.
Intelligent transport systems make their most significant contribution when active traffic management measures are implemented: Dynamic speed regulation (used to optimise traffic flow on the infrastructure), overtaking bans (active) for HGV according to the level of traffic.
In Traffic Control Centres, ITS provide operators with assistance in selecting, implementing and monitoring traffic management strategies by means of Traffic Management Support Systems. Operators have access to real-time traffic information on wall displays, video images from sections of the infrastructure equipped with cameras, and alerts in the event of an accident or incident.
ITS are also involved in the management of Traffic Control Centre data, the transmission of information between operators, the dissemination of traffic information via key partners (media, service operators etc.) and the internet, data archiving and traffic history.
In the field, active installations make it possible to:
- collect data (electromagnetic loops in the road surface, infra-red detectors, DSRC antenna etc.),
- monitor traffic and events (cameras),
- provide users with information or instructions (variable message signs (VMS), direction signs etc.),
- communicate between installations and the Traffic Control Centre (fibre optics, broadband etc.).
Produits & Services
STI en France
Strategies for active traffic management, preferential treatment for PT, management of roadworks, VMS
When traffic intensifies on both motorways and urban dual carriageways, traffic managers implement a set of measures to balance traffic supply (the road’’s capacity to handle traffic) and demand, in order to avoid congestion. To achieve this the Traffic Control Centres are equipped with strategies and resources based on the use of ITS.
The first set of measures, lane control, affects the number of lanes open to traffic either temporarily (e.g. hard shoulder running during rush hour, lanes reserved for taxis and public transport etc.) or alternately at different times of day (e.g. the reversible lane on the St-Nazaire bridge). High Occupancy Vehicle (HOV) lanes with variable charges according to the number of occupants in the vehicle, are another effective alternative for reducing traffic congestion.
The second set of measures, motorway access management, is used to manage demand on motorway entry slip roads. The system uses traffic signals to control access and is remotely supervised in real time. In practice this ensures traffic flows are regulated in order to avoid entry point congestion on the main carriageway.
The third set of measures is passenger information systems using mesh networks (primarily in peri-urban areas). These allow the traffic manager to provide users with advice on itineraries including journey times. This makes it possible to balance traffic demand across the network and avoid busy routes becoming saturated. This advice is provided via variable message signs, radio stations broadcasting travel bulletins and on the internet.
ITS are used as decision support tools for implementing and monitoring measures and for remotely controlling equipment. They are used to provide users with real-time information by means of the variable message signs and informatory signs along their route.
In urban environments, traffic demand management is handled using traffic signal control. On the city scale, specific software applications are used to manage thousands of junctions and adapt phases according to pre-established strategies (e.g. using a “green wave” to control the flow of traffic, traffic signal priority for buses etc.). These strategies help to ease congestion and reduce air and noise pollution in urban areas.
Monitoring traffic speed, flow, post incident traffic management, emergency response planning and activation, response coordination
On road and motorway networks, transport incidents rapidly hinder the proper functioning of an infrastructure both due to the congestion generated upstream and the danger it represents (risk of secondary accidents). Transport incident management is therefore a vital activity for a Traffic Control Centre; it must be both rapid and effective.
ITS make a significant contribution to meeting these objectives by providing high-performance resources at each stage of incident management: Detection, response and the reopening of the infrastructure.
Incident detection relies on Automatic Incident Detection (AID) software, which processes CCTV footage and triggers an alarm when an abnormal event is detected (accident, congestion, vehicle breakdown etc.).
Incident response and handling users requires the rapid dispatching of emergency services and equipment. These are accurately directed to the site of the incident thanks to the precise geolocation of the vehicle involved (geographic coordinates) using a satellite navigation system.
Warning and safety messages appear on Variable Message Signs located upstream of the incident, as well as on on-board satellite navigation systems, warn users of the incident ahead so they can adapt their speed or change their route. In engineering structures such as tunnels, the safety systems automatically close access when serious incidents occur inside the structure.
Finally, for major events involving a wide range of stakeholders (local authorities, managers, operators, police, fire service etc.), ITS make it possible to activate and jointly steer electronic Traffic Management Plans. These events could include motorway closure or a planned event (sporting events at the OL stadium, international trade fairs etc.).