Horn Please! Use Dipper at night!

Lorries in India are decorated quite flashy and Yankee!
They look like they draw whatever they like but actually they have something in common! Try me to find them! haha

They drive passing on the left, on the left, and on the right at like 150 km/h. "Keep distance" and "Horn Please" are obviously necessary but, to my big laugh, you often find contradictions; stop horn please. haha

I bet now you are interested in the meaning of "Use Dipper At Night"! :D Good luck finding it!