The collisions happened shortly before 7pm local time and led to a complete closure of one of the German capital’s main traffic arteries.
After the driver was detained, officers led hundreds of people stuck on the shut-down highway away from their cars.
Police used a strong jet of water to open the box he had put on the car’s roof, but found only tools inside.
Investigators did not reveal the man's identity, as is customary in Germany, but local media identified the suspect as Sarmad D.
He is under investigation for three cases of attempted murder.
There were also indications the man had mental health issues, Geisel said.
“The fact that the suspect was possibly suffering from psychological problems does not make this issue any easier,” Geisel said.
“If personal problems mix with religiously loaded ideas, this can lead to uncontrollable acts — yesterday's events have shown in a very painful way how vulnerable our society is.”
Investigators were working to determine if the suspect was linked to an extremist group or if other people were involved in his actions but so far found no indications of that, according to Steltner.