Abstract-The first edition of the Grand Cooperative Driving Challenge (GCDC) was held in the Netherlands in May 2011. Nine international teams were competing in urban and highway platooning scenarios with prototype vehicles using cooperative adaptive cruise control. Team Scoop, a collaboration between KTH Royal Institute of Technology in Stockholm and Scania CV AB in Södertälje, participated in the GCDC with a Scania R-series tractor unit. This paper describes the development and design of team Scoop's prototype system for the GCDC. In particular we present considerations regarding system architecture, state estimation and sensor fusion, design and implementation of control algorithms and implementation issues regarding the wireless communication. The purpose of the paper is to give a broad overview of the different components that are needed to develop a cooperative driving system; from architectural design, workflow and functional requirements descriptions to the specific implementation of algorithms for state estimation and control. The approach is more pragmatic than scientific; it collects a number of existing technologies and gives an implementation oriented view of a cooperative vehicle. The main conclusion is that it is possible, with a modest effort, to design and implement a system that can function well in cooperation with other vehicles in realistic traffic scenarios.