Father, toddler die in crash near Tasmanian breath test station; partner survives being flung from wreck.

Investigations are continuing into a crash which killed a 19-year-old Tasmanian father and his two-year-old daughter after their car pulled out of a line of other vehicles waiting at a breath-testing station.

Alex Peart, 19 from Midway Point, and his daughter Ruby Rose Peart were killed in the single-vehicle crash on the Tasman Highway, in Sorell, about 9:10pm on Thursday.

Mr Peart’s partner and mother of Ruby, Xanna Rose Weavell, was thrown from the car during the crash and is in hospital in a stable condition.

A friend of the couple, Tyler Williams, said all their friends were devastated.

“They were just a perfect little family everything they did they did together. It just a shocking, horrible, horrible thing,” she said.

Ms Williams said Ruby was happy and laughing all the time.

"Her mum got her a little tiara for her birthday, it was going to be a Frozen theme."

Police said they were running a static random breath testing (RBT) site on the Tasman Highway Midway Point at the roundabout with Penna Road.

Mr Peart's car stopped in the line of traffic before it made a U-turn and travelled back towards Sorell, overtaking other vehicles.

Mr Peart lost control soon after, hitting a pole, with the impact causing the vehicle to break into two.

"The rear of the vehicle remained in contact with the pole and the front came to rest in the westbound lane," police said.

Mr Peart and his partner were thrown from the front of the vehicle.

"The driver was declared deceased at the scene. The female passenger was conveyed to the Royal Hobart Hospital with non-life threatening injuries," police said.

Police are seeking information from any member of the public who may have been in the RBT line and witnessed the crash.

'No suggestion of police pursuit': Commissioner

Tasmania's Police Commissioner Darren Hine said the crash was disturbing and was now subject to a coronial inquiry.

"Obviously when someone does a U-turn before they reach a random breath test site we're [under] an obligation and it's common practice to find out why that vehicle has avoided a random breath test site," he said.

"They were following normal procedure to find out why the vehicle did actually did a U-turn at a random breath test site."

He said last night was a terrible reminder of what could happen on the roads.

"Obviously our thoughts are with the family and friends of those who were killed last night, and also the emergency services workers that had to deal with the horrific scene," he said.

"It's obviously up to the coroner to determine the facts of the matter."

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