Keeping the Buses Moving

2009-11-07

Traffic Light Priority Signalling Transceiver

A large global customer was involved in the installation and commissioning of an autobus control network in a European capital city.  Part of the project was to control traffic lights (robots) at key junctions such that the autobus could dominate priorities.

The customer required the development of a low power VHF radio link that would meet the ETS 300 133 radio specification and which could be mounted at road junctions.   The development was to include all aspects of the radio design including the electronic and hardware design together with the over-air signalling software which employed RTIG protocol traffic.
The project presented a number of challenges to the design team at Wood & Douglas Ltd.

The RF design required the radio to be fast switching between transmit and receive modes and to deliver 100mW of radio output power. 

The radio electronics had to be housed in a watertight enclosure that would be resistant to environmental changes.  

The software had to take RTIG protocol traffic to and from the roadside to the autobuses and to encapsulate this data such as to pass it seamlessly to and fro.

Extensive use was made of the W&D simulation resources to achieve these goals.  

Electronic design benefited from Microwave Office software, the housing was modelled in Solid Edge 3D modelling and the software development made use of a number of tools at the teams disposal.  
Adopting this simulation route allowed much of the design to be ‘soft’ proven before any real hardware and software was created.  This ensured a fast cost effective solution to be created for the customer and allowed a seamless evolution to the production stage. 

The product is now in high volume production in the W&D in house surface mount facility and has minimal human involvement in the testing due to the use of extensive automatic testing routines.