The attacks in Barcelona have renewed fears around the world about what has become the most basic terrorist weapon: the car.
Governments and security forces have been scrambling for months to cope with the low-tech tactic of simply driving a car or truck into a crowd of people. In the past 13 months, 125 people have died in these types of attacks in London, Nice, Berlin and now Barcelona. Most of those attacks were also carried out by individuals who had no direct connection to Islamic State or other groups and who operated largely on their own. And in the United States, a woman died after a man drove a car into anti-neo Nazi protesters during a demonstration in Charlottesville, Va., over the removal of a statue of Robert E. Lee.
"The threat picture has been going in this direction for some time in the sense of these isolated cells of two or three individuals, or one man by himself, doing some of these things," said Raffaello Pantucci, director of international security studies at the London-based Royal United Services Institute. "On top of that, it's the methodology that has now become accepted practice in launching terrorist attacks using vehicles or knives, which we all have access to."
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Many cities have been slow to react to the new threat. This spring, London's city council rejected plans for barriers along some of the city's bridges, deeming the bollards too ugly. One day after that decision, three terrorists drove a van at speeds of around 90 kilometres per hour along London Bridge, hitting dozens of people. They then crashed the van and stabbed several more in nearby restaurants and bars before being shot dead by police. A total of eight people died in the attack and more than 40 were wounded. The city council has now put up barriers along most of the city's bridges including Westminster Bridge, where a man drove a van into pedestrians in March, killing three, and then stabbed a policeman to death. Temporary barriers have also been erected during several events this summer including during the Wimbledon tennis tournament, the Edinburgh Festival and the BBC Proms music concerts.
There were virtually no obstructions along the Promenade des Anglais in Nice last year either when a man drove a truck into crowds of people watching a Bastille Day fireworks display. A total of 86 people died and more than 100 were injured. The city has now installed a series of bollards along the promenade at a cost of around $30-million.
Barcelona, too, has had no bollards or barriers along Las Ramblas, the famous street that has become the latest target of terrorists who used a van to kill 13 people there and another person at a nearby resort town. The city has put up temporary cement barriers on some occasions but there are no obstructions on the city's main strip, which is packed with tourists in the summer. However, within hours of Thursday's attack, Madrid and Bilbao began setting up barriers around some of their famous landmarks and there have been calls for Barcelona to do the same.
It's a tricky problem for many cities, balancing realistic safety concerns with the cost and public inconvenience of putting up barriers that restrict movements. The barriers installed along London's bridges can stop a 7.5 tonne vehicle travelling at around 90 kilometres per hour, but they cost around $1,000 per metre. And there have been complaints from cyclists who worry the barriers will push them into traffic and pedestrians who say they impede walkways.
"The problem is where do you stop?" said Mr. Pantucci. "Because basically everything ultimately becomes a potential target and you have to balance that up against the reality of an actual attack versus the cost of doing of it."
And the barriers might not work, he added. Terrorists "are adaptive," he said. "They have an intent in mind, a deadly intent, and they will find a way of trying to do it."
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There's also the chance these types of attacks could eventually fade away as the public become less horrified and the media coverage less intense. "Ultimately, there's a sort of mundanity to this," he said. "And [terrorists] do have to shock, they do have to awaken people. They are trying to get a message across and if you can't get a message across because everyone just becomes used to these things, and the media are not reporting it any more, then you have to do something more shocking to attract attention."
David Videcette, a former London police detective who is now a security consultant, said putting up barriers on city streets shouldn't be seen as disruptive and that Europe should have seen these types of low-tech attacks coming.
"I think that we have been very slow to respond to the changing threat," Mr. Videcette said adding that vehicle and knife attacks had been common in the Middle East for years. "In Europe, we were slow to pick up on the fact that it would come here."
He added that Britain went through a similar kind of barricading during the IRA bombings in the 1970s when buildings in central London were targeted. "We grew from that and put protection and barriers around buildings," he said. Today, he added, "we just need to look at the threat and we need to be grown up about it and say 'this is what we've got to do.'"