In the mid-Seventies, the Dutch State Railways needed new material to modernize its express passenger service. Trains with flexible utilization are required in this densely populated country in order to manage service in the urban areas. As a result, from 1977 to 1994, a total of 144 powered rail cars, the "Koploper" family, were placed into service. These powered rail cars could be quickly and easily separated and coupled at stops. It also became important that passengers be able to change from one unit to the other, when the train was in motion. The engineer's cabs were thus quickly raised up one level and these powered rail cars were equipped with crossovers at the ends. This feature gives the "Koplopers" a brawny, unusual look. The "Koplopers" were built by the firms Talbot, CEM Oerlikon, and Holec, and were designated by the Dutch State Railways as the classes 4000 and 4200, which differed from one another in their motors. A short while ago the "Koplopers" underwent modernization and were equipped with air conditioning and facilities for handicapped people. These powered rail cars can reach 160 km/h / 100 mph and are run in the classic NS paint scheme, but they have also been used as advertising surfaces such as for the Olympic Games in 2008 in Beijing. The "Koplopers" are certainly a successful development in rail vehicle technology and with their unusual looks they are clearly leaving their stamp on passenger service in the Netherlands.