Meaning per category – J
This category consists entirely of warning signs. These signs give you the opportunity to timely anticipate possible danger. Sometimes they are combined with signs from category A. This can be with both a speed limit as well as with a recommended speed.
For example, there are signs that warn about a certain condition or shape of the road:

J-1
Poor road surface

J-2
Bend to the right

J-3
Bend to the left

J-4
S-bend, first to the right

J-5
S-bend, first to the left

J-6
Steep slope

J-7
Dangerous descent

J-16
Roadworks in progress

J-17
Carriageway narrowing

J-18
Carriageway narrowing on the right

J-19
Carriageway narrowing on the left

J-20
Skidding danger

J-25
Loose chippings

J-26
Quay or riverbank

J-38
Speed bump

J-39
Retractable bollard (poller) in the carriageway
In addition to that, there are signs that warn you that you are approaching a dangerous traffic point:

J-8
Dangerous intersection

J-9
Roundabout

J-10
Level crossing with crossing barriers

J-11
Level crossing without crossing barriers

J-14
Tram (crossing)

J-15
Movable bridge

J-32
Traffic lights
Saint Andrews crosses are always placed at level crossings (indicated by signs J-10 and J-11). These indicate how many tracks cross the road. With a single Saint Andrews cross (J-12) there is just one track; with a double Saint Andrews cross (J-13) this can be two or even more tracks. In that case, another train can approach from the other direction after one has already passed.

J-12
Single Saint Andrews cross (one track)

J-13
Double Saint Andrews cross (two or more tracks)
The following signs warns you of other road users, animals and low-flying aircrafts:

J-21
Children

J-22
Pedestrian crossing

J-23
Pedestrians

J-24
Cyclists and moped riders
Do note!
Although sign J-24 only shows a bicycle symbol, it warns of cyclists, snorfietsers, moped riders and speed pedelecs. This sign is usually located at a crossing where the cycle path or cycle/moped path crosses the road.

J-27
Wild animals

J-28
Livestock

J-29
Oncoming traffic

J-30
Low-flying planes
The following signs are typically used temporarily on electronic matrix signs. This means that they only appear when the situation arises. But they can also be a standard where the situation regularly occurs, for example, where traffic jams often occur or on viaducts where there is almost always a crosswind.

J-31
Crosswind

J-33
Possible traffic jam

J-34
Accident

J-35
Poor visibility due to snow, rain or fog

J-36
Sleet or snow
If all these signs cannot represent the danger, then there is a general danger sign. The danger itself is shown on the supplementary plate:

J-37
Danger, rutting

J-37
Danger, exit construction