Bob Harvey<p><a href="https://twit.social/tags/Geograph" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Geograph</span></a> Picture of the Day <a href="https://twit.social/tags/POTD" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>POTD</span></a> from the <a href="https://twit.social/tags/Windsor" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Windsor</span></a> area, <a href="https://twit.social/tags/England" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>England</span></a> 2008 <br><a href="https://twit.social/tags/motorway" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>motorway</span></a> <a href="https://twit.social/tags/M4" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>M4</span></a> <a href="https://twit.social/tags/phantomjam" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>phantomjam</span></a> <a href="https://twit.social/tags/traffic" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>traffic</span></a> <a href="https://twit.social/tags/photography" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>photography</span></a> <a href="Https://geograph.org.uk/p/800463" rel="nofollow noopener noreferrer" translate="no" target="_blank"><span class="invisible"></span><span class="ellipsis">Https://geograph.org.uk/p/8004</span><span class="invisible">63</span></a> <br>Free to share – please credit Andrew Smith/Geograph</p><p>A Phantom Jam or traffic wave is a bunching phenomenon, caused when cars start slowing to avoid tailgating. See also <a href="https://www.livescience.com/61862-why-phantom-traffic-jams-happen.html" rel="nofollow noopener noreferrer" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="ellipsis">livescience.com/61862-why-phan</span><span class="invisible">tom-traffic-jams-happen.html</span></a></p>