Sonja Koesling reports from Northern Italy where a dynamic traffic prediction tool is making the region’s traffic flow impressively smoothly.
Covering an area of 25,000 square kilometres, Piedmont is, after Sicily, Italy’s second largest region: its provinces are intersected by more than 34,000 kilometres of main road. In order to create a sustainable and accessible mobility system on a regional level, the regional government of Piedmont decided to invest in Intelligent Transport Systems (ITS). The company responsible for managing traffic and providing mobility information in this region is 5T, a public company owned by the Piedmont Region, the City and the Province of Turin. Since autumn 2013 the company’s traffic managers have been using PTV Optima to assist them in this task: a tool that enables dynamic traffic prediction.
“5T was awarded the contract to develop a regional traffic operations centre which is based on a regional traffic control system,” says Rosella Panero, Managing Director at 5T and President of TTS Italia, the National Association for Transport and Safety Telematics. The aim was to provide real-time traffic monitoring including traffic data acquisition, processing and aggregation. Another goal was to deliver real-time data completion in order to estimate traffic states that also take areas without traffic sensor infrastructure and measurements into account. The project also focussed on alarms to be triggered in the event of anomalous traffic situations such as traffic congestion or accidents including traffic control systems informing travellers via suitable services.
“Actually, the challenge of this project is to provide a reliable centralized traffic information and management system that also covers areas outside the city boundaries,” explains Panero. “This result is achieved by merging fixed traffic sensor data with ‘virtual sensor’ data coming from different data providers and fleet managers with a monitored area which is eight times enlarged at minimal infrastructure update and maintenance costs.” Consequently, congestion on the major roads, particularly in and around urban areas, is reduced by several per cent, thus improving air quality. At the same time road safety is increased. PTV Optima is the solution that helps 5T to achieve its ambitious goals.
From offline to online
PTV Optima combines the tried-and-tested offline transport modelling method with real-time data and algorithms. This process is based on a transport model created in PTV Visum that shows each “typical day” (eg, working days or weekends) for the selected transport area. It models transport services and travel demand using demand matrices. Dynamic traffic assignment is used to calculate the time-related traffic volume and turning movements in networks based on travel demand. This is where online data comes into play. In PTV Optima, the data is used in real time in order to adjust capacity, speed and volume from PTV Visum’s base model to the current local flow and road conditions. The simulation of PTV Optima includes the network structure, traffic flow dynamics and the route choice behaviour of road users, covers the traffic situation for routes without detectors and predicts the impacts also of unforeseen incidents. “PTV Optima is the solution which best meets our requirements”, says Dr Fabrizio Arneodo, ITS Design & Development Manager at 5T.
Dynamic not static
Alongside Floating Car Data (FCD), approximately 1,400 induction loop stations as well as 200 stationary sensors, such as infrared and radar, are currently implemented in Piedmont, delivering new measurement data relating to real-time traffic patterns at 5-minute intervals. “This allows us to observe roughly one half of 76,000 arcs of our Transportation Graph. The other, much larger section of our routes is covered by PTV Optima”, explains Arneodo, adding that this is a solid base for traffic management.
Being able to predict traffic behaviour is key to ensuring the traffic management team can dynamically control traffic. PTV Optima can give an up to 60-minute forecast on the development of traffic. “Here we have opted to use a rolling approach”, says Arneodo. “That means that we simulate a 60 minute time frame which is then automatically recalculated every five minutes.” This allows 5T to see what effect the volume of traffic, speed and disruptions have on the various sections of road.
Making a difference every day
At 5T the system is generally put into action for two main applications. The first is when the traffic manager receives information from the relevant police authority regarding a traffic incident. An ‘incident’ could be an accident or even a group of demonstrators on the road. “His job is to apply this information to a specific scenario and to respond with appropriate traffic measures”, explains Fabrizio Arneodo. This could involve, for example, opening extra lanes, putting changeable message signs in place or passing information on to road users via text message, the company’s website, mobile applications or the radio.
The second application makes use of an automated feature. If pre-defined thresholds are exceeded – because actual traffic behaviour differs greatly from normal patterns – the system will send a warning to the traffic manager. This can, for example, be due to the weather.
“As we are situated next to the Alps, there are a lot of tunnels in this region which we have to close in winter during adverse weather conditions”, says Arneodo. “Closing the tunnels leads to unusual congestion patterns in the traffic network. The system recognises this change automatically and suggests an intervention strategy to the traffic manager.”
A reliable aid
At 5T intervention strategies are developed offline by traffic engineers before being applied to the PTV Optima online environment where they are assessed, compared and weighted using real-time traffic data. The engineers then share their results with the traffic managers based at the traffic management centre. They are the ones responsible for turning scenarios developed by the team into operative measures. PTV Optima aids managers in this task by making it possible to quickly return traffic to normal levels within the road network. “I like the robustness and efficiency PTV Optima is delivering reliable information”, exclaims Arneodo. “PTV Optima is an extremely sophisticated system, but it features a straightforward interface that has been developed and designed with the user in mind, making it simple for anyone to use.”