Initially there were only two pairs of trains a day on the line. From 1 August 1848, there were three pairs of trains a day for two years. The journey between Hümme and Karlshafen took between 35 and 40 minutes. In 1851 the
Kingdom of Hanover joined the
German Customs Union, so the port of
Hann. Münden, which was closer to Kassel, came to be preferred for river transport. In parallel, river traffic on the upper Weser, which was strongly affected by changes in water levels, was significantly impacted by the opening of the
Hanoverian Southern Railway in 1856 from Göttingen via Hann. Münden to Kassel. The cargo handled at the Weser quay in Karlshafen in 1863 was only 19,024 tonnes. In order to overcome the decline in traffic, an extension of the line from Karlshafen was discussed. Preliminary negotiations took place in 1864 with a British bank for financing this project, but were not completed. In 1866, following the
Austro-Prussian War, the political situation changed fundamentally with the annexation of Kurhessen and Hanover by Prussia.
Prussian period The Prussian administration had a significant impact on the
Elector Frederick William Northern Railway Corporation and hence to Carl's Railway. The company was renamed the
Hessian Northern Railway (
Hessische Nordbahn) and it planned to build a line from Karlshafen via
Detmold and
Herford to
Lemförde. On 1 April 1867, the
Northern Railway headquarters was established in Kassel. In 1868 the
Northern Railway was taken over by the
Bergisch-Märkische Railway Company (BME) and in 1873 it took over the operation of the lines. On 1 January 1882 the BME was nationalised by the Prussian government. Although the BME planned several variations of an eastward extension of Carl's Railway between 1873 and 1878, these always failed due to lack of funds. In 1873 the
Royal Westphalian Railway Company received a concession for a second line through Karlshafen. This line, the
Solling Railway, was opened in 1878 and quickly became a very important east–west trunk route for freight. It passed through Karlshafen on the eastern (or northern at this point) bank of the Weser, where a station was built, which was never connected to the Carl line on the opposite bank. In order to avoid confusion between the two Karlshafen stations, the station on Carl's Railway was suffixed
Left Bank (
Linkes Ufer,
l.U.) and the station on the Solling Railway was suffixed
Right Bank (
Rechtes Ufer,
r.U.). In the 1870s there was a modest volume of traffic Carl's Railway with two pairs of trains each day. Subsequently, there was a gradual increase to seven pairs of trains in 1914. However, this involved the increased use of mixed trains with passengers and freight with extended travel times of up to 50 minutes. Pure passenger trains took 33 minutes thanks to a speed limit of 50 km/h imposed in 1904 for secondary lines. In 1895 a halt was established between Hümme and Trendelburg in Stammen and in 1899 a halt was opened on the Wülmersen estate.
Reichsbahn period The absorption of the state railways in 1918 into the newly formed
Deutsche Reichsbahn (
German State Railroad) took place during severe political and economic crises that directly affected the Carl's line. The frequency of trains had been reduced during the
First World War and on 15 January 1924 reduced again to only three daily pairs of trains.
Multiple units took over passenger operations. The
Reichsbahn attempted to economise by closing Stammen and Wülmersen stations, or at least reduce the number of trains stopping there, which led to widespread protests. After a new examination of profitability this decision was finally rescinded. Only with the 1925 summer timetable did the situation improve. Until 1938, the frequency increased again gradually to up to seven pairs of trains a day. Some trains were operated from and to Kassel. Four pairs of trains were made up of multiple units.
Period after the Second World War Carl's line was not damaged in the
Second World War. In the spring of 1946, daily services consisted of only one pair of passenger-only trains and on weekdays an additional pair of mixed passenger and goods trains, which did not stop in Stammen. These two pairs of trains did not travel every day. From the 1949 summer timetable, there were six pairs of trains on weekdays and five on Sundays and public holidays. Some trains again ran to and from Kassel. In the 1950s, Carl's line had up to nine trains running in each direction. The running time was reduced to less than 30 minutes and many trains ran through to and from Kassel. Around 1950, the extension of the Carl's Railway to connect with the Northeim–Ottbergen–
Altenbeken line was again discussed; this would have required the construction of an approximately 530 metre-long tunnel. The unfavourable topographical conditions in Karlshafen created difficulties, however, and it was decided to cater for the north–south long-distance freight traffic on the Warburg–Altenbeken route by construction a bypass curve at Altenbeken station to the
Hamm–Warburg line. With the dieselisation of lines, passenger operations were generally carried out using diesel
railbuses. At times, class V 36 diesel shunting locomotive hauled passenger trains. From 1963 rollingstock used included
class 86 locomotives, class ETA 150 accumulators railcars with control cars, single-engine rail buses of
class VT 95 with control cars and diesel railcars of class VT 60 with control cars. Freight on the Carl's Railway at this time was limited and was handled by a
class Köf II shunting locomotive to/from Hümme station. The permissible load between Hümme and Trendelburg was 200 tonnes, on the remaining section of the line it was only 100 tonnes. Railway sidings existed in Karlshafen (Weserhafen), in Wülmersen (estate) and Trendelburg (sand quarries). ==Closure ==