you should see what happens when you activate your indicator to overtake another lorry when highways are crowded but still fluid
everyone in the middle lane is driving faster than you, so have to hit the brakes. making the people behind also having to slow down, etc
than one of those who has already slowed down to 70, moves over the left lane, where people were driving 130-150kmh
almost forcing them to make an emergency stop
5 mins later you have a traffic jam...
and it all started because the lorry had to overtake someone driving as fast as him!