Roads or highway in OpenStreetMap lingo. This layer is directly derived from the OSM road hierarchy which is why it is called highway. Only at zoom level 4 to 7 some major highways from Natural Earth are used otherwise it is only OSM data. It contains all roads from motorways to primary, secondary and tertiary roads to residential roads and foot paths. Styling the roads is the most essential part of the map. If you can put enough effort into it makes sense to carefully style each subclass. For more comfortable styling you can also just style the roads by class. Roads can have different properties, a road can have oneway=yes and bridge=yes at the same time. These properties are reflected in the field properties. This layer is not meant for labelling the roads (the purpose of the layer highway_name).

The highway layer also contains polygons for things like plazas.

Fields

class: Either motorway, major_road (containing trunk, primary, secondary and tertiary roads) and minor_road (less important roads in the hierarchy like residential or service) or path for non vehicle paths (such as cycleway or footpath).
subclass: Original value of the highway tag. Use this to do more precise styling.
properties: Additional properties describing the nature of road. The properties bridge and tunnel can be combined with oneway as well. So to style all bridges the same you should style both the properties bridge and bridge:oneway. Properties can be one of bridge:oneway, tunnel:oneway, ramp, ford, bridge, tunnel oroneway.

README.md

highway

Fields

Mapping