4 Seriously Injured in Amusement Park Accident

Four people are recovering from serious injuries after an amusement park accident outside of London.

The car full of thrill-seekers -- on a ride called "The Smiler" at Alton Towers -- slammed into an empty car stuck on the tracks Tuesday. The force of the collision wedged the cars together.

The accident left 16 riders dangling for more than four-and-a-half hours.

Walter Reiss, a roller coaster safety expert, said modern ride technology deters such accidents from happening.

"This sort of accident should never be able to happen, because there is a very sophisticated computer system that watches the location of all the trains," Reiss said.

"The Smiler" is manufactured by Gerstlauer Amusement Rides, a German company responsible for the "Pandemonium" rides at Six Flags parks across the United States. Officials at Alton Towers said in a statement that the park will remain closed "until we understand better the cause of this dreadful incident."

Statistically, amusement park rides are safe -- with the chances of being injured estimated at about one in 24 million.