Two serious accidents involving buses and trucks this week
 

The roads are very icy this week.
Snow during night, and the it starts to melt, but today it was cold again so the half melted snow turned to ice.
These conditions have caused many accidents involving trucks and buses, two of them with serius injuries and even one dead.

Bus driver dead and 22 injuried in accident involving a bus, two trucks and several cars
21/2 2017 a bus from Arlanda to Karlstad crashed into the rear of a truck on E18 close to Arboga.
The truck and several other vehicles had stopped because they met a "wall of fog". Two cars crashed into a truck. Another truck stopped at the scene. Suddenly a loud crash was heard when the bus crashed into the truck.
The busdriver, from Karlstad died in the accident and 22 other were injured.
It was dangerous conditions with dark road, heavy fog and ice on the road surface.

http://www.gp.se/nyheter/sverige/j%C...dade-1.4167546

http://www.aftonbladet.se/nyheter/a/...r-trafikolycka

http://www.expressen.se/nyheter/tota...astbilsolycka/

http://www.vf.se/karlstad/olycksbuss...-mot-karlstad/

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5 persons to hospital, one with serious injuries
Today, 23/2 2017 at around 11 a bus stopped at E18 close to Brottby in northern Stockholm because of a warning light.
For an unkown reason a truck hit the bus in the rear and then crashed through a railing and down in a ditch.
The road was closed in both direction causing major disturbances in the traffic.
Five people were sent to hospital, one of them by helicopter.
The road will close again at 21.00 when they will tow the truck.
The truck driver is under investigation for causing bodily harm and reckless driving.

http://www.norrteljetidning.se/blalj...ll-och-brottby (pics of the bus and some on scene film)

http://www.aftonbladet.se/nyheter/a/...varligt-skadad (pics of the truck)

And this newspaper tells us that a bus have crashed with a truck: :confused:
http://www.expressen.se/nyheter/just...e-med-lastbil/

Do your local authority highway services use salt or sand to combat ice?

I realise that salt doesn't work at very low temperatures (sand is better), but it sounds as though your problems were due to refreezing of snowmelt (which would be close to zero Celsius).

During the relatively severe winter of 2010, many local authorities ran short of salt (and, in addition, the sustained low ambient temperatures exacerbated the 'lack of salt' problem), leading some local authorities to experiment with additives such as molasses and other alternatives to the 'usual' rock salt (which was coarse pink halite - now 'we' use finer white salt).
The following outlines the emergency reserves held by the government (local authorities are expected to hold their own stocks locally):-
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/571267/strategic-salt-protocol-note-2016.pdf

Well they use salt and other methods. But this type of ice is hard to melt with that method if the temperature is below zero on the road surface. Actually it does not have to be very cold in the air to be very cold on the road surface.