The use of vehicles as weapons is one of the latest modus operandi of terrorists.

The most recent was the truck attack in a busy street in central Stockholm (Truck rams into crowd in Stockholm; April 8).

The worst attack last year was in Nice on the Bastille Day national holiday, at an event that was guarded by about 250 security officers (Chaos as truck mows down all in its path; July 16, 2016).

In the Stockholm attack, it was reported that the beer truck was hijacked while the driver was unloading his goods.

In Singapore, it is common to see delivery truck drivers leaving their engines running and the driver's cabin unlocked while they make their deliveries.

The use of vehicles as weapons means that attackers can kill anywhere and anytime. It must become second nature for all drivers to lock their vehicles when they leave it, even if it is for just a short time.

Also, anti-ram barrier systems, such as those at the Arsenal Football Club's Emirates Stadium in London, are worth studying. The barriers are hidden and incorporated as part of the stadium's design.

Building owners must work with Singapore's security agencies to determine what needs to be done to enhance the security of their premises.

A recent report announcing a tie-up between Nanyang Technological University and the Land Transport Authority on self-driving buses is good news (Self-driving buses to be tested at NTU; Oct 20, 2016).

But even at this stage, the Government should not discount the possibility of hackers taking over the autonomous vehicles and turning them into lethal weapons. Makers of these vehicles must have the technology to stop them.

Our security forces have been doing an excellent job in keeping our homeland safe.

However, even with effective intelligence measures to minimise the risk, we are still open to lone-wolf attacks.

We need to learn lessons from across the world, be aware and be prepared, in order to stay safe.

Loong Chik Tong