This is easy to see when cruise control is on. Many drivers are heavily influenced by the speed of other drivers. And you can also tell who else has their cruise control on. Human perception of speed changes constantly.
>>Many drivers are heavily influenced by the speed of other drivers.<<
This is true with me. One of my faults, and I admit it is a fault, is that my subconscious perception is that if I am going the same speed as everyone else, then I am standing still.