LONDON The attack on a Berlin Christmas market showed the devastation that can be wrought by the simple act of driving a truck into crowds, and the problems in preventing another massacre.
The attack in Germany on Monday, in which 11 people were killed by the truck in addition to the murder of the Polish driver, mirrored a militant raid in the French city of Nice in July that killed 86.
Hauliers increasingly track their vehicles in real time but security experts say the technology cannot be used to stop an attack if a lorry has been hijacked to be used as a weapon.
"(Militant) groups have been shouting about this sort of attack for some time, it's just that the Nice attack was the first really successful one we've seen," said Raffaello Pantucci at the Royal United Services Institute defence and security think-tank.
"Whenever you see a successful attack you will see people trying to copy it."
From a militant's perspective, the advantage of a lorry attack is its simplicity: a truck is not difficult to obtain and move around, as guns and explosives are, and it does not operate in an environment that can be secured, like the air industry.
"If you have security forces who are very aggressively keeping an eye on guns and on bomb-making stuff and you need to acquire a certain level of training to do these things, then it raises the threshold of launching a successful attack," said Pantucci.
"If you are dealing with a heightened security environment you basically use what tools you have to hand."
The threat from a lorry attack can be reduced by physical deterrents such as concrete blocks and bollards, but this is harder for temporary events like Christmas markets.
British police said in a security update after the Berlin attack that event organisers could use large vehicles to create road closures, and position machinery used for events such as electricity generators and temporary pedestrian barriers to slow down a truck.
But haulier and security industry experts say is impossible to eradicate the chance of another attack.
"Realistically, against a very determined terrorist there is no absolute defence," said Rod McKenzie, a spokesman for Britain's Road Haulage Association.
He said the industry was taking common-sense measures to reduce the risk, such as never leaving the engine running and the keys in the cab, and not falling victim to people impersonating police.
Electronic trackers can monitor the movements of vehicles in real time, which can help police if a lorry is stolen hours or days before it is used as a weapon, but he said that would not stop a hijacking.
"It's difficult to see how technology alone can stop an attack," he said. "What it can do is provide information and tracking information."
(Editing by Pravin Char)