At ACISA, we work to transform urban mobility through intelligent, cooperative, and sustainable solutions. One of our most representative projects is the deployment of a V2X-based traffic light priority system in the city of Granada.
This case study illustrates how infrastructure, vehicles, and platforms can be integrated into an interoperable ecosystem that enhances the efficiency of public transport in real time.
An interoperable, distributed, and secure V2X infrastructure
Granada has become a real-world environment for technology validation, where we have implemented a system capable of connecting buses and traffic lights through short-range cooperative communications. This makes it possible to optimize travel times, improve punctuality, and reduce emissions, fully aligned with European standards for Intelligent Transport Systems (ITS).
The technological foundation of the project is the ETSI ITS-G5 standard, a short-range communication technology that enables direct interaction between vehicles and infrastructure (V2I), without relying on mobile coverage. The entire architecture has been designed according to Edge Computing principles, delegating logic to distributed roadside equipment to ensure resilience, fast response times, and scalability.
In this environment, traffic light priority is managed through the exchange of standardized cooperative messages:
- CAM (Cooperative Awareness Message): provides information on the bus position, speed, and direction.
- SPaT (Signal Phase and Timing): communicates the status and duration of traffic light phases.
- MAP: describes the geometry and topology of the intersection so that the vehicle can interpret how to interact with it.
These messages comply with UNE-CEN ISO/TS 19091:2019, ensuring compatibility with other present and future C-ITS systems in Europe. This interoperability is a key aspect within the C-Roads program.
From Pilot to Full Deployment
The system began with a pilot test covering 15 intersections along the stretch between Avenida de la Constitución and Puente Blanco. Following its successful results, it was expanded to include 38 traffic signal intersections across the rest of Granada’s Bus Line 4.
Currently, 19 buses are equipped with V2X On-Board Units (OBUs) and operate daily on an urban network where:
- 38 RSUs (Road Side Units) have been installed.
- 38 traffic signal controllers have been upgraded with ACISA’s new M-HUB model, with each RSU directly connected to its corresponding controller.
- Each controller is centralized and managed through the Smart Mobility SATURNO platform, enabling monitoring, data collection, and remote configuration.
- Vehicles maintain constant communication with the infrastructure through CAM messages.
The system is now fully operational in both directions of the route and has been validated under real urban traffic conditions
How V2X traffic signal priority works
When a bus equipped with an OBU approaches an intersection, it sends priority request messages. The system first verifies whether the vehicle is authorized to make such a request at each crossing and analyzes whether priority should be granted. To do this, the M-HUB traffic controller evaluates several factors in real time:
- Bus position and approach to the intersection
- Direction of travel and valid trajectory
- Accumulated delay, consulted from the SAE system
- Current state of the traffic signal cycle
- Traffic conditions in other phases of the intersection
Based on this information, our M-HUB assesses the impact of a potential cycle adjustment and autonomously decides whether to grant the requested priority. This decision-making occurs within the controller itself, without intervention from the control center, minimizing latency.
In summary, the operational cycle includes:
- Detection of the bus and analysis of its route and trajectory.
- Evaluation of the priority request, taking into account the actual delay and other traffic variables.
- Approval or denial of the priority request.
- Automatic activation of the green phase or continuation of the current cycle.
Each of these actions is fully traceable, including details such as vehicle, intersection, time, reason for approval or denial, and timing information.
Saturno: Advanced monitoring and graphical configuration
The SATURNO Smart Mobility suite, also developed by ACISA, enables centralized monitoring and management of the system, while operating as a distributed system in which controllers retain decision-making capabilities.
From SATURNO, it is possible to:
- Configure information for each intersection, including its type and inventory of installed systems.
- Set up and monitor the M-HUB installed at the intersection, including sub-controller plans, statuses, and alarms.
- Define valid entry and exit trajectories for the priority system at each intersection.
- Associate these trajectories with authorized bus lines.
- Establish delay thresholds for each incoming line.
- Monitor and log all system events in real time.
- Access a detailed historical record by intersection and by vehicle.
In addition, SATURNO allows editing and uploading of MAP and SPaT messages from the TITAN software, ensuring consistency between the road geometry and the information received by vehicles
Real and measurable results
The benefits of the system are already visible. At connected intersections, buses have reduced their travel time by an average of 19.5 %. The average figures obtained are:
- Average time savings per intersection: 12 seconds
- Range of savings: 7 to 17 seconds
- Number of daily transitions per intersection: 100
- Total daily savings (across 114 intersections): over 38 operational hours
These improvements translate into:
- Better service regularity and punctuality
- Lower fuel consumption
- Reduced pollutant emissions
- Less driver fatigue and higher passenger satisfaction
A scalable system for the mobility of the future
Beyond the specific case of Granada, this deployment demonstrates that cooperative V2X systems can be implemented today effectively and in compliance with European standards.
The infrastructure is already compatible with:
- Priority services for emergency vehicles
- Hazard warnings at intersections
- Real-time traffic signal phase information for passenger cars
- Integration with autonomous vehicles
Thanks to this project, ACISA demonstrates that the implementation of V2X technologies in real urban environments is not only feasible but also highly effective. Our ability to integrate intelligent infrastructure, cooperative communication, and control platforms positions us as a benchmark in the development of advanced ITS solutions for more efficient, safe, and connected mobility.
