Various "Urban Transportation Systems" are currently in developing, in order to put forward solutions to congestion and pollution in dense areas. Autonomous electric vehicles in free-access can be seen as an attractive approach, in view of the large flexibility that can be expected. One instrumental functionality linked to this solution is platoon motion: several autonomous vehicles accurately follow a trajectory defined on a dedicated circulation lane, with pre-specified inter-distances. A global decentralized platoon control strategy, supported by inter-vehicle communications and relying on nonlinear control techniques is here proposed. In the nominal case, each vehicle is controlled with respect to the same smooth reference trajectory modelled by cubic B-Splines. This trajectory is locally modified and relayed on-line when a vehicle detects an obstacle. The trajectory distortion naturally reflects a driver's behaviour, since it consists in approximated clothoidal trajectories and the use of B-Splines ensures consistent connections. Experimental results, carried out with several urban vehicles, demonstrate the capabilities of the proposed approach.