« To deal with this congestion, ISPs had to come up with a way to keep the internet running without slowing everything down So they reconfigured their motorways by introducing ‘priority lanes’ for certain types of internet traffic. Internet traffic can be thought of as being represented by different types of vehicles. Activities like streaming video are the lorries and take up a lot of space, whereas emailing or browsing are smart cars and much smaller ». (via Ofcom | What is internet traffic management?)