After the terror attack at a Christmas market in Berlin, many people were asking themselves if sensitive in-vehicle security systems could not prevent such catastrophes.

Now, it appears, the security features in the truck did indeed prevent the worst from happening. A joint investigation  of the German public broadcasters NDR and WDR, together with the daily "Süddeutsche Zeitung" came to the conclusion that the trucks automatic brakes stopped the attacker from killing many more people.

The incident showed that, in principle, it is possible to use a truck or a car as a weapon and to kill people. But it also revealed that active security systems pay off: They work, and they can save lives.

How does a modern truck brake?

Many security systems in trucks are required by law. Those include the anti-blocking system (ABS). It prevents the wheels from blocking on slippery and icy roads. In addition, there are more advanced electronic brake controls, which help further reduce the braking distance.

The truck that the terrorist stole in Berlin was made by Scania. It's Electronic Breaking System (EBS) has advantages over the conventional hydraulic brakes. Traditionally, the brakes at the different axles responded with a delay, when the driver hit the breaks. In the case of a long truck, this can make quite a difference. EBS activates all brakes exactly at the same time - giving the driver more control over his vehicle.

Such breaking systems are among the safety-features, which the driver can not overrule or shut down.

Can the truck brake by itself?

Emergency Brake Assist (EBA) is required by law in all newly registered trucks in the EU since 2013. Scania calls its system Advanced Emergency Brake (AEB).

The system is mainly intended for situations on highways and freeways. When the distance to the car or truck driving ahead is getting too short, the system will first warn the driver with a visual or acoustic warning signal. If the driver does not react and the distance gets even shorter the truck will automatically reduce the speed - to a standstill.

But the driver has the ability of overruling the system. Usually hitting the gas pedal is sufficient. The reason: The system could wrongly identify something as an obstacle that is not one. Then, the driver has to make the decision.

A typical situation for this is a car, parked at the side of a narrow and winding road. The robotic system would normally believe that the road is blocked, but the truck driver knows, that he can get past. By hitting the gas he disables the brake assistant and continues his journey.

But, if the sensors do notice a collision they will overrule the driver and activate the breaks. Apparently, this is what happened at the Berlin Christmas market.

What systems protect pedestrians?

For speeds below 30 kilometers (or 20 miles per hour), there is a system called "city safety": It warns the driver of collisions with pedestrians and bicyclists. Such warning systems are usually combined with robotic assistants for dangerous situations at street intersections or at a turn-off, where bicyclists or pedestrians are in danger of getting into the blind spot of the driver. A typical situation often resulting in accidents: The truck takes a sharp turn, while the driver overlooks a bicyclist approaching on a bicycle path from behind parked cars.

Also, such systems recognize cars approaching an intersection from the side. Many such systems also include cameras, which enable the truck driver to look around his vehicle at corners, which he would usually not see - for example when driving backwards. And radar sensors measure the distance and speed of objects around the vehicle. In all those cases, however, it is the driver who takes the final decision, whether to stop or not.

What if the truck gets off track?

Then tracking assist helps. The system is meant to alert the driver, if he falls asleep or is distracted and not focused on the road. An alert includes vibration of the steering wheel and influencing the steering to make sure that the truck stays inside its lane. This can prevent possible lurching of the truck after the driver makes a sharp steering motion to correct his earlier mistake. But, in case the driver actually wants to leave his lanes, he can overrule tracking assist with a decisive move of the steering wheel.

Is it possible to prevent a truck from being started by unauthorized people?

Trucks for dangerous goods and tourist buses are often equipped with a system called Alcolock. Those are devices which measure the alcohol level in the breath of the driver. The truck can only be started after someone who is completely sober blows into the device.

Otherwise, a simple rule applies: Whoever has the key (either mechanical or electronic) will be able to start and drive the truck. Theoretically, it would be possible to build a system which requires a fingerprint or an eye scan similar to Alcolock. But such inventions have not proved marketable.

Is it possible to shut down a truck, if the driver ignored mandatory rest periods?

No, the digital Tachograph which is required within the EU, registers driving and rest period as well as speed, but it does not have any influence on the controls of the vehicle. This is not perceivable for good reason: If a truck driver gets into a traffic jam, through no fault of his own, he can not take his required rest stop but must still be able to move the truck forward and out of the way.

Can you disable a truck by remote control after a theft?

Theoretically this would be possible. Some companies have developed such systems, but they are not legal everywhere. Such systems are typically designed to prevent a truck ignition, but once the motor is running and the vehicle is driving it would be too dangerous to interfere into the vehicle controls by remote control. Logistics companies rather use GPS tracking to follow stolen trucks.

Can autonomous driving be of help

It is not clear when and if fully autonomous trucks will be driving on our highways. When they hit the road, it is most likely, such projects will start with routes that are clearly defined and mostly include well known freeways and short access roads to large logistics-centers.

Besides that, it is perceivable, that there is a combination of autonomous driving with a truck driver present in the cabin. Such a driver would always be able to turn of the autopilot.

Then, what's all the technology good for?

It's about safety. In Germany alone, trucks today transport about 60 percent more cargo than they did in the early 1990s. In practice there are almost no goods that do not at least spent part of their way to the customer on the road. Trucks are an essential part of modern logistics.

In the same time period, regarding fatal incidents involving trucks: The number of severely injured people went down by 40 percent. The number of people killed is now about half of what it was about 20 years ago.

Will it ever be possible to prevent the abuse of trucks?

If a determined culprit is eager enough, he will probably always find a way of committing crimes with vehicles. Even in an unlikely science fiction scenario, where all trucks are fully autonomous, controlled by satellite and driving around only on clearly defined surfaces, a killer may still find a way of doing it. Maybe next time, it won't be a truck but a construction or agricultural vehicle. Bulldozers, for example, will certainly never have a built-in anti collision system.