Transcript for New terror warning from the TSA

Next tonight here, the new terror warning from the TSA after a growing number of terror attacks using vehicles for mass murder. The concern now, trucks being rented here in the U.S. You'll remember this searing image of one of those worst attacks in nice, France. It's a method ISIS has been calling on its supporters to adopt. Why the warning now in this country. ABC's senior justice correspondent Pierre Thomas. Tonight, the TSA warning commercial trucking and rental companies about the increasing threat of using tractor-trailers and other huge vehicles, including buses, as tools of terror. Since 2014, 17 vehicle ramming attacks resulting in 173 fatalities with 667 wounded. In December 11 murdered as this large truck ran over pedestrians at an outdoor Christmas market in Berlin. And by far the most deadly, the nice, France, truck rampage that massacred 87. This is a very significant challenge for law enforcement driving a truck into a crowd. It's hard to stop every one of those attacks. Reporter: For months, ISIS has been calling on radicals to commandeer vehicles to run over people. It's working, and it doesn't just involve big vehicles. Last month, an assailant in London used a rented SUV to fatally run down three people before stabbing a police officer to death. David, tonight near at trump tower, you can see the large sanitation trucks set up to guard against this threat. The TSA is urging large trucking and rental companies to quickly report any stolen vehicles and any suspicious activity. David? Pierre, thank you. Next to the severe storms

This transcript has been automatically generated and may not be 100% accurate.