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Fascinating maps from the Transport for London archives show how the capital's Tube lines have evolved over the last two decades.

The collection of diagrams, which were used inside the train carriages, reveal changes to the network dating back to 1995.

Maps were altered over the years as new stations were built or the lines were extended.

The archives show some interesting tweaks to the design of the diagrams, with different iconography introduced or the colour of the lines adjusted.

New map icons

The archives show how Tube station icons on maps from the late 1990s featured a different way of highlighting interchange stops.

Tube enthusiasts will notice two small lines pointing up and down at each interchange stop around this time.

These showed the different lines passengers could change to at the stop, indicated by colour.

Transport YouTuber and commentator Geoff Marshall told the Standard the lines were discontinued in order to "simplify" the Tube signage for commuters.

Mr Marshall said the decision was a "design choice". He explained that the additions to the station icons were originally part of the Johnston typeface, designed by Edward Johnston in the early 1900s.

But after TfL took over responsibility for the London Underground, they tried to simplify signage, Mr Marshall said.

"[The interchange lines] just added clutter, so it wasn't easy for people to make fast changes," he said.

Two-way maps

In the early 2000s Tubes featured both left to right and right to left versions of the line maps, the archives show.

Transport for London introduced the mirror maps as a trial, a spokesman told the Standard.

They were placed on trains according to which direction they were travelling.

However, the scheme was later dropped as trains sometimes turned around or entered service the wrong way, the spokesman said.

The below example from August 2006 shows the Bakerloo line starting from both Harrow & Wealdstone and Elephant & Castle.

Central line changes colour

The maps show the colour of the Central line changed slightly between 2003 and 2004.

TfL suggested that the alteration was made because it changed the colour formation of its standard red colour at the time.

The National Rail logo and text also changed shade around the same time, a spokesman said.

Jubilee line extension

Significant changes to the Jubilee line maps were seen as the service was extended to Stratford during the late 1990s.

A map from January 1999 showed all the new stations, but they were charted along a dotted line as the service was still under construction.

The maps continued to evolve until the line was eventually fully opened for service in October 1999.

Notably, on the 1999 maps, North Greenwich was named "North Greenwich for the Dome", directing commuters to the Millennium Dome - now known as The O2.

New stations

The archives also reveal the introduction of new stations, including Heathrow Terminal 5 on the Piccadilly line.

Maps of the line showed the new station from February 2008 in preparation for the opening of the terminal at the end of March 2008.

Wood Lane station also appeared on Circle, Hammersmith & City and Central line signage after it was opened in 2008.

Transformation of the Circle line

Finally, the maps show how the Circle line was at one time circular.

Following an extension that opened in 2009, Circle line trains could continue from Edgware Road to Hammersmith.

This meant that the line, which once orbited the capital, was no longer in the shape of a complete circle.

The Circle line now runs in a spiral shape from Hammersmith to Edgware Road, then looping around central London back to Edgware Road.

The change was made to improve reliability and capacity, and increase the service frequency to Hammersmith.

Jon Hunter, Head of Design at TfL, said: “TfL’s iconic Tube map design is widely recognised around the world. As the network grows and becomes more accessible, we are regularly changing the maps and signage in stations and on Tube carriages to keep them up to date.

"With the introduction of the Elizabeth line next year, as well as our wider plans to make more stations step-free in the coming years, we are already looking at how we make further changes to these important wayfinding signs to help customers travel on our network as easily as possible.”