New possibilities for traffic signal priority requests

For many years, local analogue systems were commonly used for traffic signal priority. Buses and trams communicated
directly with the traffic signal controller, generally via signal-point based requests triggered as the vehicle approached the junction. While these systems were fast, reliable and independent of central networks, they have now reached their technical limits. In addition, the analogue radio frequencies used are increasingly needed for new digital applications. To support the move towards digitalisation, INIT offers a local solution for digital, wireless priority requests.

Vehicles are equipped with a V2X On-Board Unit (OBU) that enables them to send digital messages to traffic signals. Using a V2X (Vehicle-to-Everything) interface, the OBU communicates with other vehicles, roadside infrastructure such as signal controllers, or even wider networks. Via this air interface, the V2X OBU exchanges information with the V2X RSU (Road-Side Unit, the traffic light’s radio communication device) installed at the traffic signal. The INIT COPILOTpc on-board computer or EVENDpc on-board computer with ticket printer continues to manage vehicle localization and the ITCS connection.

A vendor-neutral PTX interface (PTX = public transport to everything) links the on-board computer and OBU, allowing
real-time data such as vehicle position and request commands to be processed. This means public transport companies are already digitally connected and independent of analogue radio technology. Such local systems with V2X on-board units are already in use or planned in Hamburg and Heilbronn / Germany, among other places.

With the increasing digitalization of transport infrastructure, centralized traffic signal priority systems are gaining
in importance. Here, the bus does not communicate directly with the traffic signals but sends its position data to a
central platform that evaluates the data, determines whether priority should be granted, and transmits the request to the relevant signal controller.

With LIVEtsp, INIT provides a modern and secure solution that requires no additional hardware in either vehicles or at signals, provided reliable mobile network coverage is available.

Real-time vehicle data, including GPS position, is transferred to the back-office system via open interfaces over the mobile network. If no on-board computer is installed, vehicles can instead be equipped with a smartphone or tablet using the LIVE Driver Terminal app. Requests are transferred directly from the LIVEtsp back-office system to the traffic
control computer or local traffic signal controller via server-to-server communication. Priority can be assigned based on predefined parameters such as occupancy level or route weighting. Public transport companies can monitor priority requirements and adjust control parameters easily using a web browser, and intersections can be configured and controlled via a web-based interface. Centralized INIT systems are already in use in Magdeburg and Ingolstadt, Germany as well as in Turku, Finland and Denver, USA.

Digital traffic signal control is a key factor in an important transport trend, Cooperative Intelligent Transport Systems (C-ITS). In C-ITS environments, connected road users (including private transport) and the transport infrastructure exchange digital radio messages, combining local and centralized approaches via standardized communication between vehicles and infrastructure. For traffic signal priority requests, buses ‘talk’ to traffic lights via digital radio protocols (mobile radio/V2X).

C-ITS enables prioritization not only for buses and trains, but also for emergency vehicles and bicycle traffic – a step towards a networked, multimodal smart city with MaaS (Mobility-as-a-Service) offerings. Using INIT solutions for traffic signal priority, public transport companies are already taking steps towards this connected future.

Whether through local digital V2X OBU systems or centralized control, INIT’s solutions enable public transport companies to digitally speed up bus and light rail services and improve punctuality. Both approaches can also be combined: for example, a central system may be used for an entire light rail line, while a local solution supports critical intersections. Hybrid models combine the advantages of both: network-wide optimization with centralized systems, and resilient, location-based capability via local systems.

Modern traffic management and C-ITS architectures are increasingly moving towards this hybrid approach. The use of digital traffic signal control – and hybrid models in particular – is shaping a modern public transport infrastructure that delivers smoother, more punctual and more sustainable mobility.