since 1960, marks were used to identify stations that offered connections with British Rail (now National Rail). The following shapes have been used: Circle (one for each line or station, where convenient) – standard default mark Circle (one for each station) – 1938 experimental map Diamond (one for each line) – early 1930s Square – interchange with British Railways, 1960–1964 Circle with a dot inside – interchange with British Rail, 1964–1970 Since 1970 the map has used a reversed (red on white) British Rail "double arrow" beside the station name to indicate main line interchanges. Where the main line station has a different name from the Underground station that it connects with, since 1977 this has been shown in a box. The distance between the Tube station and the main line station is now shown. Contemporary maps have marked stations offering step-free access with a blue circle containing a wheelchair symbol in white. Stations with links to airports (Heathrow Terminals 2 & 3, Terminal 4, and Terminal 5 for Heathrow Airport and the DLR station at City Airport) are shown with a black aeroplane symbol. Since 2000, stations with a nearby interchange to river bus piers on the Thames have been marked with a small boat symbol to promote London River Services. When Eurostar services used , the Eurostar logo was shown next to Waterloo station. In November 2007, the terminus was transferred to St Pancras International. Lines or services The Tube map aims to make the complicated network of services easy to understand, but it is not possible to have complete information about the services that operate on each line. Limited-service routes have sometimes been identified with hatched lines, with some complications added to the map to show where peak-only services ran through to branches such as that to Chesham on the Metropolitan line. The number of routes with a limited service has declined in recent years, as patronage has recovered from its early-1980s low. As there are now fewer restrictions to show, most of the remaining ones are now indicated in the accompanying text, rather than by special line markings. Official versions The Tube map exists to help passengers navigate the London rapid transit network, and whether it should play a wider role in helping people navigate London itself has been questioned. The question has been raised as to whether mainline railways should be shown on the map,