To what end do many semi-trucks' front tyres have spikes?

The front tyres of semis are sometimes equipped with spikes to improve traction on slippery roads.

Wheel spikes are used on semis in some climates to combat the icy

and slippery conditions that can arise on the roadways during the winter.   

These wheel spikes, when contacted by the road,

produce tiny bits of ice that act as traction for the tyres.

In addition, wheel spikes have little effects on performance and fuel economy when driving on dry roads.

The main goal of installing wheel spikes on a vehicle is to increase its stability and security on snowy roads.