It was at 19.40 that the accident occurred on the E18 in Karlskoga in the direction of Örebro.
The truck driver is now suspected of having caused the accident.
– The classification of the crime is not observed sufficiently far and it is an offense with a fine, says Torbjörn Roos, commander on duty for the police region Bergslagen.
The driver of the a-tractor had to be taken to hospital by ambulance. The extent of the damage is unclear.
The road is said to be open to traffic at 20.50.