To Buffer or not to Buffer!

Many are too optimistic that they'll be "getting things back on track" if something goes wrong in a project.

I realized many years ago on their way into Yugoslavia from Austria, that it is good with buffers along the way in a schedule. Do not put a little buffer in the end - at the time, you've already lost.
In Austria they give you security against brake problems like this:

In Yugoslavia (dengang!!) Did like this:

Which model do you like best?