Signs have subtle differences in colouring and fonts. One notable exception to this is that hazard warning signs in the Republic are amber diamonds. Since the adoption by Ireland of metric speed limits, warning signs have been placed on either side of the border to alert motorists to the change to or from miles or kilometres per hour. As the United Kingdom does not use the euro, advertised prices for service stations and shops will change currency on crossing, although many places along the border will accept cross-border currency informally (albeit usually at a rate favourable to the trader). Other typical signs of crossing a European border are also noticeable. These include subtle differences in the paving materials of road surfaces and pavements, sometimes with visible differences in colour between materials across the border, changes to street lighting when crossing the border, (though these also vary across inter-county borders), and changes in the colour of postboxes (green in Ireland, red in Northern Ireland). By rail, there is no immediate sign of crossing the border, but the trackside mileage markers change from Irish-style markers at the post (from Dublin Connolly railway station) to black-on-yellow markers, common to the United Kingdom, at the post, between Dundalk and Newry stations. As in most places, radio signals from the cellular networks on both sides of the border often travel several kilometres (a few miles) across it. This was a source of annoyance to those resident in border areas when roaming charges were incurred with most service providers if the phone connects to the "wrong" network when making or even receiving a call. Inter-member mobile phone roaming charges were abolished in the European Union from 15 June 2017. , it remains to be seen whether this arrangement will continue after Brexit. "Puckoon" is a comic novel by Spike Milligan, first published in 1963. It is set in 1924 and details the troubles brought to the fictional Irish village of Puckoon by the Partition of Ireland when the new border passes directly through the village. It was later made into a film in 2002. In the 1980s, Colm Tóibín walked the length of the border, later releasing a travel book entitled "". Following the Brexit vote in 2016, a mockumentary about a fictional post-Brexit border patrol named the "Soft Border Patrol" was produced by the BBC. In 2018, an anonymous Twitter account called @BorderIrish gained notability tweeting as the Irish border in the first person, and the implications that Brexit would have for it. The following cities, towns and villages are located on the border or not far from it (listed from Lough Foyle to Carlingford Lough):