Starting from a fully bright LED followed by a tail of different brightness LEDs shifting left & right with a calculated speed is the real effect of knight rider running lights.
The trail consists of six brightness levels & it has maximum length of 12 channels to move both sides.
Duty cycles in the fade trail.
1% = Very dim
5% = Dim
10% = Dim average
25% = Less bright
50% = Medium bright
100% = Full bright
The circuit contains with a minimum of parts & can be add more LEDs to make it wider length by using an external driving transistor per each channel.
Schematic
