At least twelve people have died in traffic over the past five days.

Four people died in a single accident on the night between Sunday and Monday, when their car collided with a tree and caught fire.

Several severe motorcycle accidents also occurred this weekend, with four fatalities.

Two men in their fifties died on Thursday. One of the men died after a car crashed into a motorcycle motorcade outside of Arvika in central Sweden. The other accident occurred when a car and three motorcycles were in a head-on collision in Växjö, in the south of Sweden. Four others were injured, one gravely.

A 50 year-old woman died on a motocross bike in Dalarna on Friday night. The regional newspaper Dalarnas Tidningar writes that the woman died after driving straight into a tree.

On Sunday night a motorcycle driver was killed after colliding with a moose, just outside Gothenburg.

“This is a very high number of deaths in such a short period,” Claes Tingvall, traffic safety officer at the Swedish Transport Administration (Trafikverket), said to news agency TT.

He notes that many of the accidents seem connected with the holidays, that none have involved families travelling in cars, that high speeds seem to have been a factor and that circumstances have been unusual.

“These accidents show up around this time of the year, in connection with these kinds of holiday weekends.”

“It has nothing to do with regular traffic,” he said. “This is unusual traffic.”

At least six of the deceased were sitting in cars travelling at high speeds, that caught on fire. Tingvall emphasized that he wasn’t referring to these specific accidents, but said that in general high speeds are often involved when today’s relatively safe cars go up in flames.

“It generally requires a great deal of energy, in other words high speed, to get a car to catch fire. Severe deformations are also necessary,” he said.

Tingvall explains this year’s increase in traffic deaths, saying that last year had an extremely low total, partly due to the severe winter weather and lower traffic volumes.

He believes more will be killed in traffic accidents in 2011 than in 2010.

“That’s practically to be expected.”