Green Light Optimal Speed Advisory (GLOSA)

Green Light Optimal Speed Advisory (GLOSA)

GLOSA provides vehicle drivers an optimal speed advice when they approach a controlled intersection equipped with traffic lights. Based on information on the phases and timing of traffic lights, speed change advisory can be offered to vehicle drivers or vehicle controls on the approach of and departure from a signalized intersection. The service aims to create an eco-friendlier and energy-efficient driving experience for vehicle drivers by providing speed advice, traffic light information and countdown to green/red, aiming to reduce energy consumption and lower the number of stops.

Participating actors in GLOSA include vehicle drivers who wish to reduce fuel consumption and increase travel comfort, public authorities who aim to reduce CO2 emissions and increase traffic efficiency and safety, road operators who wish to increase traffic efficiency and safety, and service providers who collect and process data, in order to provide the most appropriate advice to drivers always prioritizing safety.

The objective of GLOSA is to enhance traffic flow and comfort, as well as to reduce emissions and fuel consumption.

Taking into account various stakeholders’ views, a list of business model blueprints that address current or future challenges of urban areas, together with their operating and value-capture scenarios depicting the inner-workings of the business models, and the exchange of costs-benefits among stakeholders, have been created for the GLOSA service.


In case of ITS-G5 communication technologies updated information related to the traffic light phase and timing could be provided from traffic management system server to Roadside stations. Such information shall then be transmitted to approaching Vehicle stations. An On Board Unit (OBU) is used which receives optimal speed profiles from Roadside Units (RSUs). In the OBU speed advice is calculated and displayed to the driver.


In case of cellular communications, information should be broadcasted from a server, for example a service provider server, to drivers’ personal information devices. The relevance area shall allow matching to a specific road section or specific lane, if the provided traffic light phase and timing is lane specific. A personal information device is used where speed advice is calculated, with regards to the transmitted optimal speed profiles, and displayed to the driver.

Detailed information about GLOSA architecture can be found here.

Physical architecture diagram - C-MobILE

Suppliers of components and solutions for the GLOSA service include research institutes, such as CERTH-HIT, CTAG, as well as private companies, such as NeoGLS, IDIADA, Dynniq, Traffic Technique,and Swarco.

Within the C-MobILE project the GLOSA service is implemented in seven Deployment Sites: Barcelona, Bordeaux, Copenhagen, Newcastle, North Brabant, Thessaloniki, and Vigo.

In Barcelona the GLOSA service is implemented based on cellular communication technology. This service covers over 20 signalised intersections of the busiest roads in the city. Applus IDIADA is the service provider which works with traffic light information from the traffic management centre of the City Council and provides it to the drivers through an App.

In Bordeaux GLOSA and SVW are implemented using both cellular 4G and ETSI-G5 communication technologies. A total of 588 intersections are configured and available to the 4G users in Bordeaux and its surroundings. Gertrude provides the timing information in real time. The 11 RSUs deployed in the city centre are also broadcasting MAP and SPaT information for intersections close to them. The service provider for GLOSA is NeoGLS and the service is available through the App “CTD – Connected Mobility”.

In Copenhagen the GLOSA service is implemented using cellular communication technology. The service provides speed advice for users so to be able to catch the green light at intersections ahead. Time-to-green and Time-to-red information is sourced in the Traffic Light Controllers and published by the local geo-messaging server in the appropriate messaging and communication standards to allow service providers and App developers to provide the information to their users. In Copenhagen, this same service is specifically tailored for optimal use by cyclists. Because cycling traffic is a more flexible mode of transport than motorized vehicles, making it easier for each cyclist to adjust their own speed and, unlike cars, less dependent on the speed of other road users in front and behind, the GLOSA service works better for cyclists especially with a lower saturation levels of the service among users.

In Newcastle the GLOSA service is implemented via both ITS-G5 and cellular communication technologies. The ITS-G5 service covers 18 signalized intersections on a key route heading north out of the city centre. This new deployment builds on an existing ITS-G5 installations covering 21 intersections in the east of the city. The new deployment is used by Arriva express buses to enable more efficient fleet operation and more reliable journey times. Siemens UK is the service provider in collaboration with Newcastle City Council and Zircon (HMI designer). Siemens UK and Zircon have also designed and implemented a 4G cellular deployment at one intersection on the same route in collaboration with NeoGLS. Newcastle City Council and Siemens are considering to expand this service through the whole route. This service is for users of the cellular bundle (currently NEAS and some private motorists) delivered to the App provided by NeoGLS .

In North Brabant the GLOSA service is implemented using both cellular and ETSI-G5 communication technologies. This service covers a several signalized intersections of the busiest roads in the city of Helmond.

In Thessaloniki the GLOSA service is implemented using cellular communication technology. The service covers a number of signalized intersections in the city centre as well as in the western entrance of the city. The Hellenic Institute of Transport (CERTH-HIT) is the service provider in cooperation with local traffic lights operators (Traffic Technique, and Swarco Hellas) for traffic lights information exchange and afterwards provision of information to drivers through the App provided by CERTH-HIT (

In Vigo the GLOSA service is implemented using cellular communication technology. This service provides information related to phase and timing of 95 intersections in the city via CTAG GeoServer  in such a way that drivers using the App can be informed on the current and future status of the traffic light of the headed intersection.