When traffic lights turn green and you cross, do you wonder what controls the timing of changes?
In the UK, trunk roads are the responsibility of national governments or their appointed representatives, while other roads are the responsibility of local authorities. In addition to maintaining road safety, these organizations all contribute to ensuring efficient traffic flow. They purchase and deploy various sensors that help determine traffic conditions and provide services to inform and manage traffic, for safety and efficiency. The market for equipment and services is heterogeneous, but coordination requires the integration of systems and standards.
A set of British standards called UTMC (Urban Traffic Management and Control) enabled these system integrations. The timing of the traffic light cycle can be changed based on knowledge of traffic conditions. Traffic light systems often have dedicated induction loop sensors, which can be very localized, but standards allow integration with a wider set of information from different sensors and systems. Traffic signal optimization algorithms have been used for decades, but traffic signals on some major strategic corridors still operate independently of each other by default, and a lack of coordinated progress through the signals can cause excessive delays . Some local authority systems can detect this and take action to improve traffic flow. Automated license plate recognition camera systems calculate anonymized travel times by recognizing the same vehicles passing through two locations; this data feeds into rules-based systems and can trigger actions, including changing the timing of traffic lights to give more green time to a strategic traffic corridor, with an overall reduction in travel times.
The timing of traffic lights can also be usefully influenced by knowledge of predicted events. Local authorities can enter a calendar of major events and schedule automated traffic management strategies to suit anticipated traffic patterns. Ray King from Newcastle City Council told us about the automated strategies used when Newcastle United FC play at home: “With an average attendance of over 50,000 people, home games can put a huge strain on the transport network. ” An automated strategy detects certain speeds, traffic volumes and gaps between vehicles, and changes the timing regime of traffic lights to help traffic exit the congested area.
Ray even noted the impact of football scoring on travel times: “If Newcastle lose, fans will start leaving the stadium earlier; if Newcastle win, fans will leave the stadium later. Traffic managers can adjust the activation of the strategy according to the score line. A 3-0 home win [removing the need to intervene] is a rare event; however, our traffic managers are eternally optimistic!
Car park systems are also integrated – occupancy sensors are common and traffic light timing changes can be triggered based on the detection of higher levels of car park exits, also useful after a major event. Weather and air quality (measured or even predicted) can also be triggers.
European cooperation at the service of standards and open data
European countries have been collaborating on road traffic data exchange standards for decades, with considerable deployment, not least due to the demands of European legal regulations over the past 10 years. In the early years of the current century, a methodology was adopted that has stood the test of time – to separate information models from specifications of implementing technology, the first realized using a well-defined metamodel and the latter automatically generated by formal mappings. This allowed the investment in common information models to be fully reused without rework as encoding and exchange preferences expanded or changed, starting with SOAP and XML to now also support REST, JSON and ASN.1 for example. The UK continues to be an active participant in this European standardization which has produced data interchange specifications for traffic situations and states, electronic signs and signals, parking, road traffic management plans, re-routing , synchronization of traffic lights, charging of electric vehicles and traffic rules.