#Geograph Picture of the Day #POTD from the #Windsor area, #England 2008
#motorway #M4 #phantomjam #traffic #photography Https://geograph.org.uk/p/800463
Free to share – please credit Andrew Smith/Geograph
A Phantom Jam or traffic wave is a bunching phenomenon, caused when cars start slowing to avoid tailgating. See also https://www.livescience.com/61862-why-phantom-traffic-jams-happen.html