Activity Field 5, related to the Locomotive Interoperability by means of remote control procedures, was one of the first to be completely finalised. The goal was to show how a locomotive or a driving trailer can remotely control another locomotive, through the standard TCN train bus (IEC 61375-1), using standard procedures as defined in UIC 556-647 (EU Remote Control). This was possible in the past only by means of proprietary solutions, often using specific cables with more than one hundred wires, each dedicated to a well-defined function. Therefore two locomotives could control each other only if they were equipped with the same product and they, and all intermediate coaches, were cabled with the required dedicated wires. So, a need for a common standard solution arose and was addressed preliminarily by the ROSIN project (FP4) and now by TrainCom (FP5). Validation activities occurred in different countries, involving a number of different locomotives:,1) Italy (Verona), on 29 July 2003, with loco E464 and loco E412 from Bombardier Italy ,2) Austria (Wien), on 25 September 2003, with loco 1142 from Elin and driving trailer 80-33 from Siemens,3) Italy (Mestre), on 29 November 2003, with loco E402A from AnsaldoBreda and driving trailer Z1 from Firema The last two events, which included a short test journey on normal tracks, were public demonstrations and were attended by a number of people external to the project, both railways and industries, including participants from Czech Republic and India. All events followed a common test procedure, which was articulated basically in three main steps:,a) the locomotive is tested against a vehicle simulator, which is able to exchange control data according to standard procedures, as though it was a second locomotive hosting a reference implementation. Target of this step is the validation of the software implemented on the loco under test from both the functional and UIC conformance points of view;,b) the second locomotive or driving trailer is then tested in the same way; at this point, if tests are successful, both vehicles are supposed to speak exactly the same language;,c) finally, the two vehicles participating in the test are coupled together, via TCN, and allowed to speak directly each other, with one of them controlling the other one; it is now possible to run the train from the leading vehicle, controlling remotely the locomotive on the opposite site. A first benefit of the system is quite apparent: when a train arrives in a station and needs to reverse its direction, it is no more necessary to decouple the leading locomotive and couple a new one on the opposite side, but is now enough that the drivers change their location, e.g. from the locomotive to the driving trailer on the opposite side, and the train can start again immediately (push-pull operation). This allows to spare personnel for coupling and decoupling locomotives and avoids the use of one more locomotive. A less common situation occurs when a train gets an assisting locomotive in front of it: it is not necessary to have also an additional driver.,The fundamental benefit is the enhanced flexibility allowed by locomotive interoperability: as all vehicles are interoperable, different combinations of vehicles are possible, allowing for optimised management of the fleet of locomotives and driving trailers. A benefit which is not so easy to catch is the capability of the TCN network and the UIC 556/647 profile to interface any kind of vehicles regardless their Human Machine interface. Existing Human Machine interfaces aboard locomotives range from full electromechanical device implementations like the OeBB's 1142 to the more sophisticated implementation showing one (driving trailer 80-33) or two (E412 and E464) intelligent displays substituting traditional instrumentation. Other differences between the vehicles involved are the use of incremental (E412, 80-33) vs. proportional (E464, 1142) input devices (direction setting, max speed set point, effort setting, etc). While waiting for the harmonisation of circulation rules at European level, also for conventional trains, the presently available Human Machine interface solutions have to fulfil the country specific circulation rules. The performed validation demonstrated how the system can take care of harmonising all such differences, hiding them below the standard procedures and allowing for seamless operation between different kinds of vehicles. Preliminary versions of the TrainCom solution have being used in normal operation since some years, e.g. in Austria and Italy. Now it can be easily adopted by other railway operators, in all countries, contributing to the interoperability of the European Railway system. Perspective for the future include further development of UIC647 (e.g. to consider trains with distributed power, like ETR460 and ICE3) and a connection with train-ground communication to allow intelligent remote supervision (to be addressed in an FP6 project). The system represents one of the main results of the TrainCom project, which includes four more activity fields, in the area of TCN conformance testing, train-ground communication, dynamic passenger information and maintenance. For more information, visit the project web site at http://www.traincom.org or enquire at e-mail: firstname.lastname@example.org.