Thanks Kalle thanks for the advice.
I am not sure how to apply suggested expression, to be specific on which property,( I supposed position)? I try to solve these problem by creating mask with same shape as truck path and then I have copied mask path to triangles position properties (I also chang transform > auto orient > orient along path). But that solving the problem only for one triangle If i repeat proces on other triangles i end up with bunch of triangles on one spot making a circle because of same keyframe properties that I have apply. If you have some more time to reply and try to explain me how to offset the timing with and expressions using layer index (index*full circle/30) I’d appreciate.