A fatal car ramming in a crowded German city square has refocused attention on the use of vehicles by people seeking to attack the public.

The incident in downtown Mannheim took place on the Monday of regional Carnival celebrations. It followed weeks of warnings that potential terror attacks could take place during Germany's pre-Easter festival period.

But the attack does not appear to be motivated by political or religious factors, and authorities are exploring the suspect's mental health as a possible factor.

Yet the choice of a vehicle as a lethal weapon in this incident and in fatal attacks in Munich and Magdeburg in recent weeks leaves open the question: why the car?

Cars are useful, but their size, speed and maneuverability also make them potentially deadly.

While uncommon as a weapon, in recent years they have been more frequently used to kill or maim people. Cars became prominent as a terror weapon during a series of incidents in Israel amid ongoing conflict with local militant groups during the early 2010s.

The use of vehicles to ram public spaces was supported by the Islamic State group in the mid-2010s. In Europe, attacks in Nice — where 86 people were killed in a truck attack — Westminster Bridge in London,

© Deutsche Welle