Governments ought to offer less generic reactions to the forms terror is taking. Of the three U.K. attacks this year, two started as attempts to mow people down with vehicles. This is an increasingly frequent terrorist practice, which has recently yielded gory results in Nice, Columbus and Berlin as well.

At least this part of the attacks (though not the subsequent knifings) could have been prevented or at least mitigated by modern technology known as autonomous emergency braking. This is generally a life-saving technology that has been shown to reduce rear-end collisions by 38 percent, and that, in its current forms, will stop a vehicle before it hits a pedestrian. In Berlin, the truck used by Anis Amri to plow into a Christmas market last December was equipped by an AEB system; it ultimately stopped the vehicle, preventing more deaths than the final casualty count of 12. The reason it didn't stop earlier is that the driver can ignore the system's initial warning, overriding it for a short while; in such a scenario, brakes are only applied after the collision.

The European regulation, adopted in 2012, required that all new vehicles come equipped with AEB starting in 2015. It decrees that the driver should be able to shut off the automatic braking function. The latter wasn't a problem in Amri's case -- he apparently didn't even consider whether the Polish-owned truck he had commandeered was equipped with the anti-collision system. But regulators would clearly make life much harder for terrorists planning to weaponize vehicles if they required that the systems couldn't be manually overridden when a collision with a human is imminent. That wouldn't make cars more dangerous: Current technology allows the vehicle to "see" the full range of options in a dangerous situation more effectively than a human driver can.

The EU regulation was a major step forward (in the U.S., automakers have agreed with regulators they would equip every new car with AEB only by 2022). Before it entered into force, only some 32 percent of new cars sold in the Netherlands, 25 percent in Germany and 21 percent in the U.K. came with autonomous emergency braking. Banning manual overrides would be another useful step.

David Fuller's view

With or without increased terrorist attacks Autonomous Emergency Braking (AEB) systems seem like an inexpensive partial solution to loss of life due to runaway vehicles.