Bombs have been terrorists’ choice of weapon in more than half of the attacks on public surface transportation around the world since 2004, according to the Mineta Transportation Institute’s news release.

They have also caused more than 60% of the resulting fatalities and more than three-quarters of the injuries.

In the third of a series of studies on the frequency and lethality of such attacks between January 2004 and December 2021, the MTI’s latest report, "The Use of Explosive Devices in Attacks on Public Surface Transportation: Trends in Frequency, Lethality, and Prevention," examines the way bombs were used in 3,836 attacks on passenger train and train stations, buses, bus stations and stops, passenger ferries and terminals, rail infrastructure, and operating and security staff.

The attackers almost always used bombs alone, but sometimes also in combination with other weapons, such as firearms. 

The attacks killed 7,412 people and injured 21,847, an average of 1.9 fatalities and 5.7 injuries per attack. Notably, bombs are also more likely to be used in attacks in developing countries than in more economically advanced countries. 

Perspective from Report's Authors

“While the percentage of bomb attacks globally has decreased, we found that lethality has increased, particularly in economically advanced countries, where suicide bombings are the most lethal bomb attacks," said author Brian Jenkins. "Most frequently, bombs were placed inside bus or train compartments, on railway tracks, or inside train stations. The bombs in stations and compartments resulted in the most casualties. However, the majority of attacks in economically advanced countries are unsuccessful, with devices discovered, malfunctioning, or failing to detonate. Despite the decrease in attacks, bombs do remain very lethal—particularly in confined spaces."

The report shows that bombers had greater success in other countries, with vehicle-borne explosive devices (VBIEDs) being the most lethal in developing countries, followed by suicide attackers carrying bombs. 

Co-author Bruce Butterworth said this may be because explosives are easier to acquire in less developed countries or detection and prevention by authorities are weaker.

“Worldwide, successful bombings have declined. More bombs are being detected before detonation, particularly in the advanced countries, although the identity of most of the individuals who have found bombs and stopped attacks is unknown," he said. "Of those who foiled attacks in those countries and whose identities are known, 40% were passengers, citizens, or employees, while the percentage in the less-developed countries was only 21%. The proportions in the two country groups were reversed for security, police, and military officials."

MTI added that, worldwide, bombs placed in railway tracks are not very lethal, as they are usually intended to cause disruption.