A double-track railway usually involves running one track in each direction, compared to a single-track railway where trains in both directions share the same track. Overview In the earliest days of railways in the United Kingdom, most lines were built as double-track because of the difficulty of co-ordinating operations before the invention of the telegraph. The lines also tended to be busy enough to be beyond the capacity of a single track. In the early days the Board of Trade did not consider any single-track railway line to be complete. In the earliest days of railways in the United States most lines were built as single-track for reasons of cost, and very inefficient timetable working systems were used to prevent head-on collisions on single lines. This improved with the development of the telegraph and the train order system. Operation Handedness In any given country, rail traffic generally runs to one side of a double-track line, not always the same side as road traffic. Thus in Belgium, China (apart from metro systems), France (apart from the classic lines of the former German Alsace and Lorraine), Sweden (apart from Malmö and further south), Switzerland and Italy for example, the railways use left-hand running, while the roads use right-hand running. However, there are many exceptions: in Switzerland, the Lausanne Metro and railways at the Germany border area use RHT as well as all tram systems. In countries such as Indonesia, it is the reverse (right-hand running for railways and left-hand running for roads). In Spain, where rails are RHT, metro systems in Madrid and Bilbao use LHT. In Sweden, the tram systems in Gothenburg (except for an Angered station and stations with island platforms), Norrköping and Stockholm (except for Alvik - Alleparken section) are RHT. The railroads (and the metro) use LHT in general, but in Malmö they use RHT due to the connection to Denmark. In Ukraine, some sections of Kryvyi Rih Metrotram use LHT due to tramcars having doors only on right side, which makes it impossible to use RHT at stations with island platforms. On the (pre-1918) French-German border, for example, flyovers were provided so that trains moving on the left in France end up on the right in Germany and vice versa. In the United States, three Metra commuter railroad lines formerly owned by the CNW near Chicago operate as left-hand running, a historical oddity caused by the original