In the last three years, at least 173 people have been killed and more than 700 wounded in 17 ramming attacks around the world (source: http://www.latimes.com/nation/la-na-tsa-truck-warning-20170505-story.html).
Apart from being a tragedy on an individual level, the attacks also affect public life. The freedom to meet is a cornerstone in a civilized society.
A lot of (often temporary) anti-ram systems and safety barrier are now being installed. Most, if not all, of these systems are aesthetically unpleasing and their sole message is that there are crazy individuals in society!
The proposed "Sit-in" system has the same primary function as the present anti-ram systems but also carries a friendly message to sit down, initiate a dialogue - and work things out!
"Sit-in" can be made in different designs and sizes taking advantage of the progress of modern concrete technology and 3D printed molds.