This work presents the design and realization of a modular antenna system composed of three co-located antennas working in the 2.4 GHz band. Two directional antennas are used for controlling train integrity through wagon-wagon communication, whereas an omnidirectional one, cross-polarized with respect to the other two, is adopted for exchanging positioning data between the train and the intelligent poles located along the railway. The gain and the radiation efficiency for the directive antennas are 5.4 dBi and 79.3%, whereas for the omnidirectional one are 4.2 dBi and 97.8%, respectively. Moreover, the effects of environmental effects on the antennas are valuated, i.e., the presence of dry and wet dust, and the prototyping of an ad-hoc case is shown in order to act as a radome against the atmospheric conditions.