  Detecting and characterising vehicles is one of the purposes of embedded
systems used in intelligent environments. An analysis of a vehicle
characteristics can reveal inappropriate or dangerous behaviour. This detection
makes it possible to sanction or notify emergency services to take early and
practical actions. Vehicle detection and characterisation systems employ
complex sensors such as video cameras, especially in urban environments. These
sensors provide high precision and performance, although the price and
computational requirements are proportional to their accuracy. These sensors
offer high accuracy, but the price and computational requirements are directly
proportional to their performance. This article introduces a system based on
modular devices that is economical and has a low computational cost. These
devices use ultrasonic sensors to detect the speed and length of vehicles. The
measurement accuracy is improved through the collaboration of the device
modules. The experiments were performed using multiple modules oriented to
different angles. This module is coupled with another specifically designed to
detect distance using previous modules speed and length data. The collaboration
between different modules reduces the speed relative error ranges from 1 to 5,
depending on the angle configuration used in the modules.
