Upon the electrification of the Amsterdam tramway network, all tram line were given a line number and a line colour. The latter designator is a square logo next to the line number, so that people who cannot read the line numbers can still recognise the line. The tram stop signs also display the line colours, as did the early twentieth century horse tram lines. Line colours have been used in other cities in the Netherlands (The Hague, Rotterdam, Utrecht), but outside Amsterdam the colours have since been removed.