Through-roads, i.e., trunk roads and motorways, are exclusively intended for high-speed travel from A to B (flow function) and are only accessible for fast traffic.
Motorways consist of at least 2x2 lanes and the driving directions are always physically separated, generally by a median strip and/or guardrail. On the right side, motorways usually have a wide emergency lane and a wide clear zone. The standard speed limit on motorways is 100 km/h during the day (6 - 19h) and 130 km/h in the evening and at night (19 - 6h). Deviations from this standard speed limit are made at a number of locations, for example for reasons of road safety or the environment. At those locations a speed limit of 80, 100 (also at night) or 120 km/h at night applies. The local speed limit may also depend on, for example, whether or not the rush-hour lane is open. In specific circumstances such as traffic jams, road works or bad weather, the speed limit may be temporarily reduced and the adjusted limit displayed on the matrix signs above the road. Trunk roads consist of at least 2x1 lane and usually have a speed limit of 100km/h.
Trunk roads are generally less safely designed than motorways and have, for example, narrower lanes and less wide clear zones. From a Sustainable Safety perspective, physical separation of driving directions is desirable on trunk roads because head-on crashes at driving speeds higher than 70km/h often have a fatal outcome. In practice, however, there are also trunk roads without physical separation of driving directions, but with a double continuous line with a green space between the lines.
Intersections with and between motorways are always grade separated. In principle, intersections between trunk roads should also be grade separated, but in practice this is not (yet) always the case. Intersections between trunk roads and distributor roads are also preferably grade separated, or else signalised.