A study of terrorist attacks that took place on passenger rail and bus systems in modern developed countries between 1970 and 2020 has found that more than 60% of incidents occurred during off-peak hours.

For the Mineta Transportation Institute’s latest Peak Hour Study, security experts Brian Michael Jenkins and Bruce Butterworth analysed more than 500 attacks on passenger rail and bus systems over 50 years, to develop a resource for risk professionals who are responsible for security planning on public transport networks.

Terrorists time their attacks to occur not only during weekday rush hours, but also during peak travel times associated with holiday travel. The 1980 bombing of the Bologna train station was one such example. The bombing occurred on a Saturday at the beginning of the traditional August holiday, when the station was filled with holidaymakers heading for the coast or mountains. Eighty people were killed in the attack.

The pattern of attacks on train targets is quite different from that of attacks on bus targets, with far more bus attacks occurring during non-peak hours, according to the study. Almost all fatalities in weekday bus attacks occur in the peak traffic hours. In contrast to train attacks, attacks on bus targets in the afternoon rush hour are more lethal than those in the morning rush hour.

They found that 19% of attacks occurred during peak hours, and that peak-hour attacks were 4.5 times more lethal than those carried out during off-peak hours.

“It seems logical that terrorists seeking to cause maximum disruption or mass casualties would launch their attacks during times of day when passenger traffic is at its height,” Jenkins explained. “Right-wing extremists and jihadists are the most lethal attackers, even without considering the five attacks that killed so many, such as Bologna in 1980, Madrid in 2004 and London in 2005. If we include those attacks, peak hours become 34 times more lethal than non-peak hours.

“However, some attackers – left-wing groups and Basque separatists, for example – have avoided large-scale casualties and have generally carried out their attacks during off-peak hours, often at night to avoid detection. Although the Provisional Wing of the Irish Republican Army was capable of carrying out deadly attacks, PIRA bombings of transportation systems, were aimed primarily at disruption.”

The UK was found to have suffered the highest frequency of attacks (19% of the total), followed by Spain (16%), clearly reflecting the terrorist campaigns by the Provisional Wing of the Irish Republican Army, PIRA and the Basque separatists, ETA. Most of the attacks in the US, the third-ranking country (with 11%), were carried out by criminals or mentally unstable attackers rather than terrorists.

“Attacks by mentally unstable individuals may have no discernible pattern and in general, the perpetrators are far more likely to be victims than victimisers. There is a need for far more proactive alerts and treatments for these individuals, rather than punishment,” Butterworth added.

Given the ease of acquiring automatic and semi-automatic weapons in the US, it is not surprising that 14 of the attacks were armed assaults, explosives were used in 11 attacks, and 8 involved stabbings, representing more than 60% of all attacks.

The study identifies what appears to be a growing level of anti-social violence carried out with physical force, knives and automatic or semi-automatic weapons on trains and buses and at stations and stops

“This is a disturbing trend that US authorities must contend with while keeping an eye on terrorists,” Jenkins said.

Attacks on operating staff and security personnel constituted a very small percentage of the total attacks (there were 19). The distribution between peak and non-peak hour attacks is similar to that for all attacks: a quarter during peak hours and just over half during non-peak hours – reflecting a common scenario in which adversaries enter a station or depot and then attack a staff member or security official.

Butterworth concluded: “We hope that the forensic detail and the way in which we have analysed and quantified the data associated with attacks on public transport during rush hours will help anyone involved in ensuring that passengers are safe.”

Counter-terrorism police in the UK have issued a number of warnings of the increasing threat of self-radicalisation since the beginning of lockdown, while Pool Re recently warned that the gradual return to crowded spaces may present a target which has not been present for over a year.


Chart: Fatalities during weekday time blocks (Source: Mineta Transportation Institute)

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