CROCS : Controller to Roadside Open C-ITS standard

Product Overview

Connecting vehicles to infrastructure through co-operative intelligent transport systems (C-ITS) enables the rapid exchange of messages between traffic management systems and vehicles and has the potential to deliver significant improvements in safety and traffic flow.

Work undertaken by the UK Department for Transport (DfT) identified barriers to the deployment of C-ITS in UK local authorities. A recurring observation was the need for interoperability between the roadside device, that communicates with vehicles, and the roadside device controlling the traffic signals.

With little or no interoperability between C-ITS components, UK highways authorities are restricted in their ability to add C-ITS functionality to their existing traffic control systems: this risks delaying the acceptance and uptake of C-ITS


In late 2016 the DfT funded the development of an open standard interface for the exchange of data between a traffic signal controller and a roadside radio unit transmitting using the European (ETSI) standard ITS-G5.

The work was undertaken by a group with considerable experience of Intelligent Transport Systems comprising IDT, telent Technology Services, Centaur Consulting and White Willow Consulting.

The work was funded through a DfT Transport Technology Research and Innovation Grant (T-TRIG) and the scope of the project was focused on two of the principal C-ITS message types: SPaT and MAP.

C-ITS dataflows

SPaT (Signal Phase and Timing) is a standard for a C-ITS message which will inform drivers about the current status and a prediction of the future stage timings of the traffic signal ahead.

MAP is a description of the physical geometry of one or more intersections which can be transmitted to a vehicle.

Implementing SPaT/MAP on traffic signals means that drivers can be advised of a speed to travel through traffic signals that will minimise both delays and emissions.

Benefits for highways authorities

CROCS helps highways authorities protect their current investments in traffic signal controllers. CROCS is simple enough to be implemented in many existing controllers: a CROCS-compliant controller will then be able to exchange SPaT/MAP C-ITS data with a CROCS-compliant roadside communication device.

How do I use CROCS?

CROCS is an open standard and is in the public domain. It is free to use and implement in any appropriate product. The CROCS documents are currently published on this site (although this may change). A useful starting point is the CROCS Data Dictionary.

How is CROCS licensed?

CROCS is published under the Open Government Licence. You are encouraged to use and re-use the Information that is available under this licence freely and flexibly, with only a few conditions.

CROCS downloads
Description Version Date Location
CROCS Data Dictionary Draft 0.1 06/02/2017 View/Download (PDF)
CROCS Schema (PDF) Draft 0.1 06/02/2017 View/Download (PDF)
asn1.xsd Draft 0.1 06/02/2017 View/Download
CROCS-0-1.xsd Draft 0.1 06/02/2017 View/Download
crocs.wsdl Draft 0.1 06/02/2017 View/Download
ITS-Container.xsd Draft 0.1 06/02/2017 View/Download
REG-D.xsd Draft 0.1 06/02/2017 View/Download
REGION.xsd Draft 0.1 06/02/2017 View/Download


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