Glatteis is formation of black ice on the roads and you spread sand/ salt and/ or other abrasives to get better traction.

see
http://www.usroads.com/journals/p/rmj/9712/rm971202.htm
"ABRASIVES

Sand and other abrasives improve vehicle traction on snow- and ice-covered roads. They can be used at all temperatures and are especially valuable when it is too cold for chemical de-icers to work. Sand is the most common abrasive, but slag, cinders, and bottom ash from power plants are also used. "

In the US, it is usually the responsibility of the homeowner to maintain his driveway and the sidewalk around him free of ice. I think they are referring to something similar.

Hope this helps

(salt-free) "abrasives" should work in that context.
The ice is "abgestumpft" with the use of "abrasives" instead of being melted by salt or other chemicals.

**Abrasives**, such as sand, cat litter and saw dust, are used to create traction on icy walkways when used alone or in combination with chemicals.
http://www.mwmo.org/education.html

The maintenance crews will make every effort to open all state highways to traffic as soon as safely possible.
The application of **abrasives**, abrasives with melting agents, or the direct application of deicing or ant- icing agents
may be applied to roadways in controlled quantities as may be mandated by CDOT maintenance supervisors to conform with local environmental laws, guidelines, or recommendations.
www.dot.state.co.us/Publications/PDFFiles/deicers.pdf

I would paraphrase it like that