The results of temporal displacement were to put it best: wild. First, the coils would glow in a fluorescent blue. Internal diodes would flash faster as well as the flux capacitor. A bright blue field of energy would form at the front of the vehicle. At 88 mph, the entire car would vanish in a flash of blinding light and the sequence would be complete.
From an observer outside the vehicle, the car would seem to explode in a large cloud of particles and leave two trails of fire in its wake. From inside the vehicle, a flash of light would appear in front of the windshield and the resulting landscape in front of the DeLorean would change instantaneously as a result of time being reversed or forwarded.
Interestingly, the fire trails would continue into thin air, as when the DeLorean was struck by lightning while flying and when it crossed the open Shonash Ravine. The Jules Verne Train created similar effects, but it is unknown whether it left a trail of fire behind.
On the opposite end of the temporal displacement, in the arrival time, three consecutive flashes would occur, announcing the incoming vehicle. Each flash was preceded by a halo that condensed to form the flash. On the third flash, the time machine arrived covered with a thin layer of ice which in most cases melted away shortly after, as an opposite to the fire trails left behind in the departure time.
Behind the scenes
To create these visual effects on screen, there was a mixture of live filming and months of post-production at ILM.
For example, the fire trails were created by laying out a chemical compound in two strips on the street and lighting them. Other effects on the car itself were produced by remote triggering. The breaking of the time barrier was signaled by a white light that flashed at that instance.