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 the support of the European Regional Development Fund (ERDF) granted by ELY Centre.

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 favouring 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 moved forward from there to  Savilahdentie  and Puijonlaaksontie. However, 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.

Adaptive control is based on the fact that the modelling knows where every means of transport in the area is at all times, not only on the fact that the vehicles are detected at the sensors installed on the road. The change is significant, as the traffic lights no longer change their control when a vehicle is detected entering the intersection. Instead, the modelling strives for the best possible implementation of the pre-set transport policy priorities at all times throughout the controlled area. In the background, the system’s algorithms calculate different options for controlling the traffic lights and always choose the best control for the situation at hand.

Adaptive control does not include fixed pre-planned programmes such as conventional traffic light control. The system automatically adjusts the operation of the traffic lights. 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 modeling also recognizss traffic disruptions and long-term changes in traffic, and can change the control without separate, laborious reprogramming of traffic lights.

Once the entire area to be controlled has been modelled, the flow of public transport, for example, can no longer be controlled in such a way that the means of public transport can pass through one intersection smoothly, but in such a way that public transport remains exactly on its schedule all the time.

Adaptive traffic control also fully supports new technologies. Mobile applications and on-board equipment can be used to identify special groups whose traffic flows or, for example, to minimise stops, to provide their own steering policy weighting factors. Such groups can be cyclists and mobile applications, which are favoured at the intersections of cycling routes, or heavy traffic, whose unnecessary stops at intersections can be avoided with predictive control. This leads to a significant reduction in transport emissions. Virtual emission modelling can even be used as a basis for a traffic light missile to minimise traffic emissions.