What is the minimum required distance between two warning triangles when placed behind a broken-down heavy truck on an open rural highway curve?

1. One triangle placed 50 to 100 metres behind, and a second triangle placed up to 150 metres back before the start of the curve/hill crest
2. Both triangles placed directly touching the rear bumper
3. One triangle placed on the front hood only
4. Triangles are only required for passenger cars