Question

The head lights of a distant car do not produce interference pattern. Why?

Answer 1

Because car headlights are not coherent, nor of a single frequency. In order to get interference you need monochromatic light with a coherence length greater than the path differences involved. Headlights are white - wide spectrum light, with no particular coherence. Thermal headlights will have no coherence at all, led headlights a tiny coherence