ISIS and Al Qaeda have specifically called for the type of attack that just happened in New York City

Terrorist groups have long been calling for supporters to attack "infidels" with vehicles, and these types of attacks have become increasingly common in recent years.

Eight people were killed and 11 were wounded Tuesday when Sayfullo Habibullaevic Saipov, who pledged loyalty to the terrorist group ISIS, mounted a curb in a rented pickup truck and tore down several blocks of a popular bike path on Manhattan's west side. It was New York City's deadliest terror attack since September 11, 2001.

ISIS and Al Qaeda have publicly called for supporters to use vehicles as weapons.

The Institute for the Study of War noted in a 2014 report that ISIS spokesman Abu Mohammad al-Adnani instructed supporters in a speech in September of that year.

He said:

"If you are not able to find an IED or a bullet, then single out the disbelieving American, Frenchman, or any of their allies. Smash his head with a rock, or slaughter him with a knife, or run him over with your car, or throw him down from a high place, or choke him, or poison him."

And a 2014 ISIS video aimed at French-speaking recruits encouraged supporters to attack people in France with cars and other easily accessible weapons.

"If you are unable to come to Syria or Iraq, then pledge allegiance in your place - pledge allegiance in France," a French ISIS member says in the video. "Operate within France."

The man then goes on to mention cars specifically: "There are weapons and cars available and targets ready to be hit. ... Kill them and spit in their faces and run over them with your cars."

Al Qaeda has also put out global calls to attack Westerners with cars.

In the second issue of its English-language magazine Inspire, the terrorist group referred to pickup trucks as "the ultimate mowing machine."

"The idea is to use a pickup truck as a mowing machine, not to mow grass but mow down the enemies of Allah," the magazine article states.

ISIS, in particular, has increasingly been relying on external attacks as it has been losing territory in the Middle East.

When the terrorist group first rampaged across Iraq and Syria claiming territory, it encouraged supporters to travel to the Islamic State, but recently ISIS rhetoric has shifted to focus on encouraging people to mount attacks in their home countries.

Sometimes these attacks are directed by ISIS leadership, but sometimes they are carried out by lone actors who don't have any significant contact with ISIS members.