Since vehicle-to-infrastructure (V2I) communications require a major initial outlay and continuous maintenance, they have been less frequently implemented than vehicleto- vehicle (V2V) communications in applications in the field of Intelligent Transportation Systems (ITS). Nevertheless, making use of the information provided by the infrastructure - traffic signals, traffic panels, and so on - can help improve the performance of various ITS applications. The present work describes the design and implementation of a low-cost infrastructure network based on ZigBee technology to alert drivers (or even override them by using active safety systems) in the case of some unexpected circumstance on the road so that they can prepare for the appropriate handling of their vehicles. Its implementation as an auxiliary network within a larger communications scheme allows the network's load to be reduced and its performance to be improved. The proposed architecture was tested on a real car in a real scenario with quantified results for different applications.