Traffic lights

Adaptive traffic light control in Kuopio

As part of the Intelligent Transport Infrastructure in Kuopio project (Kuopion älykäs liikenneinfra, KÄLLI), adaptive traffic light control was introduced in Kuopio in 2021 and 2022 on Tasavallankatu, Savilahdentie and Puijonlaaksontie, as well as on Saaristokatu, Leväsentie and Volttikatu. A total of 21 intersections are connected to the adaptive system. System adjustments are still in progress.

Locations of the adaptive traffic lights

The KÄLLI Project

The Intelligent Transport Infrastructure in Kuopio project (KÄLLI) succeeded in improving the flow of traffic, movement and parking and reducing energy consumption and emissions. The project invested in adaptive traffic light systems, intelligent parking management systems and bus information displays. Studies were carried out on the measurement of traffic and the development of the city bike system, among other things. 

The project lasted from spring 2020 to the end of 2022. The project’s budget was EUR 836,400, of which 70% was funded by the Centre for Economic Development, Transport and the Environment (ELY-keskus) as part of the European Regional Development Fund (ERDF). 

Procurement and objectives of the adaptive system

The City of Kuopio acquired the system from Dynniq Finland Oy (nowadays Swarco Finland Oy). The value of the purchase of the system was approximately EUR 176,000. The city received 70% ERDF support for the investment. 

The adaptive system was introduced at the highest traffic volume intersections in Kuopio, from the intersection of Tasavallankatu and Jynkänkatu all the way to the intersection of Puijonlaaksontie and Mallitalontie. The objective of the system is to reduce delays. 

According to a study conducted in Tampere, the introduction of an adaptive system reduced delays by 15% compared to traditional traffic light control. Delays were reduced for both pedestrians and vehicles. Reducing delays also reduces emissions. No research data is available on the reduction of emissions. 

Public transport

The system will help in prioritising public transport. Public transport routes are programmed into the system in advance. The system can provide benefits to buses in such a way that the delays of buses are minimal throughout the route, which passes through the adaptive area.

Implementation of the system and adjustments

The implementation of the system began in the spring 2021 from Tasavallankatu and proceeded from there to Savilahdentie  and Puijonlaaksontie. However, occasional adjustments are still required. 

Adaptive system operation

Traditional traffic light control focuses on controlling one traffic light crossing. The sensors at the intersection detect approaching vehicles and try to extend the green light so that the vehicle can pass through the intersection smoothly. In traditional control, the beginning of the green light can be brought forward, and the end can be extended based on predefined programmes. The objective is to design the programmes so that they work well throughout the life cycle of the traffic lights. 

In adaptive traffic control, traffic light control operates with a background system modelling the entire controlled area. This background system is informed of the control principles, transport policy and the desire to control traffic. 

The basis of adaptive control is that the modelling tracks the location of every vehicle in the area in real time, whereas traditional control models can only track vehicles in the immediate vicinity of that intersection. The change is significant, as the traffic lights no longer change their control when a vehicle is detected entering the intersection. Instead, the modelling takes the traffic flows of the entire area into account and always seeks to provide the best traffic flow for the area as a whole, in accordance with pre-set priorities. The system’s algorithms constantly calculate different options for controlling the traffic lights and always choose the best control for the situation at hand. 

Adaptive control does not utilise the fixed pre-planned programmes that conventional traffic light control does. Instead, the system automatically adjusts the operation of the traffic lights, so it is no longer necessary to separately define for the system when there is a morning rush hour, a public holiday or, for example, a significant event. The system’s modelling also recognizes traffic disruptions and long-term changes in traffic, and can change the control without separate, labour-intensive reprogramming. 

Adaptive control allows the traffic lights to be controlled in a more holistic and consistent way to improve traffic flow over a wider area. For example with public transport, whereas traditional control systems can only give buses priority access in a certain intersection once the bus has arrived at that intersection, an adaptive control system can give buses uninterrupted priority access through the entire control area. 

Adaptive traffic control also fully supports new technologies. Mobile applications and on-board equipment can be used to identify special groups who require different weighting in terms of traffic flow, for example by minimising stops. Some potential use cases include providing cyclists with priority access at the intersections of important cycling paths, or minimising unnecessary stops for cargo traffic, using proactive traffic light control. Using measures like these, in combination with virtual emissions modelling, adaptive control systems can provide a significant reduction in traffic emissions.