Vehicle exterior aerodynamics directly influences the performance, safety as well as passenger comfort of a road vehicle. Of the various kinds of trailers that can be attached to a car, caravans are most frequently employed. Caravan towing can represent a significant part of the annual mileage, hence a detailed study of the flow structure of the car and caravan combination becomes inevitable. In this work, a steady three-dimensional simulation of the flow-field around a car-caravan combination with and without a drag reduction device has been carried out. Changes in the flow structure brought in by the attachment of a caravan to a car have been studied in detail. The flow phenomenon was investigated using the general-purpose commercially available CFD code ‘Fluent’. Conclusions are drawn based on the analysis and a drag reduction device was incorporated as a design modification.