Västra Götaland police said they had no information about why the 22-year-old was walking on the motorway.
An elderly couple was also hit by a car that fled the scene. The man and woman, both in their 80s, were found 14 metres apart after the hit-and-run on a road in Blekinge county. They have been taken to hospital
Also in the south, an older man was hit in the face by a rocket.
"A rocket failed to launch so he went up to it and then of course it went off," Skåne police spokesperson Calle Persson told TT.
There were reports of minor fires, most caused by errant fireworks, across the country, while a car slammed into a bus stop in a Stockholm suburb.
Police described the night as relatively calm but said calls about drunken fights increased after midnight.
A spat in central Stockholm lead to one man being taken to hospital after he was knifed at around 2am in the Östermalm neighbourhood. The police have opened an investigation into attempted manslaughter and said the victim should be well enough to be questioned early on Tuesday.
Just after 3am, further south in the Stockholm suburb Årsta, a drunk driver lost control of their car and slammed into a bus stop. None of the people waiting for the bus were injured but the driver was taken to hospital.
Police in Malmö, meanwhile, intervened after reports of gun shots in an apartment. No one was hurt but the police are looking for the bullet.