Thank you for the nice feedback :) 

Concerning the arrow colors:
The little rotation arrows would suffice to indicate in what direction the direction arrows are going to rotate when a bus drives over them. But I thought it might be helpful to also use different colors: The yellow direction arrows always rotate clockwise, the white ones always rotate counterclockwise.

Especially in more complex levels the colors might be helpful: When your solution failed, but you are sure that a part of your solution was correct, you can quickly recunstruct this part in your next attempt by remembering to put a white arrow here and a yellow arrow there etc.