Public security

It’s nearly impossible to stop terrorists from using trucks as weapons. Here’s what cities are trying.

Nice, Berlin, London and now Stockholm. Over the past year, terrorist attacks using vehicles have become a sad fact of life in Europe. Such attacks are obviously appealing to would-be mass murderers: In most European nations, a truck is far easier to acquire than a firearm or explosives, and sometimes even deadlier. Groups such as the Islamic State and al-Qaeda have taken note, specifically suggesting that a car could be a good weapon to harm civilians.

For authorities, the attacks represent a major problem. Guns and explosives can be banned, but motor vehicles are vital for many city-dwellers. So how do you protect a city from an attack like this? There is one commonly used solution, but it’s far from perfect.