The first <a href="https://en.wikipedia.org/wiki/Traffic_light" id="mwfw" rel="mw:WikiLink" title="Traffic light">traffic lights</a> are installed, outside the <a href="https://en.wikipedia.org/wiki/Palace_of_Westminster" id="mwgA" rel="mw:WikiLink" title="Palace of Westminster">Palace of Westminster</a> in London. Resembling <a href="https://en.wikipedia.org/wiki/Railway_signal" id="mwgQ" rel="mw:WikiLink" title="Railway signal">railway signals</a>, they use <a href="https://en.wikipedia.org/wiki/Railway_semaphore_signal" id="mwgg" rel="mw:WikiLink" title="Railway semaphore signal">semaphore</a> arms and are illuminated at night by red and green <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Gas_lamp" id="mwgw" rel="mw:WikiLink" title="Gas lamp">gas lamps</a>.