Aerodromes - Visual Aids, Markings and Signs — Page 405, Lesson 554

Let's pick up with the markings that govern where you may and may not go on the ground — the road holding position markings, and then the two surface markings that replace signs when a sign just can't be installed. First, the road holding position markings. These are to be provided at all road entrances to a runway. So if a road — a public or service road — leads onto a runway, you'll find these markings painted across the road at the holding position. And here's the key detail: they're marked in accordance with the local road traffic regulations. That means the exact style of marking follows the rules of the country where the aerodrome sits, not a universal ICAO standard. So as a pilot, you treat that road marking as a holding point — you don't cross it without clearance — but its physical appearance is governed by local road law. Now, the mandatory instruction marking. This is the surface-painted version of a mandatory sign. When it's impracticable to install a physical mandatory sign — say, there's no room for a signpost — the mandatory instruction is painted directly on the taxiway pavement. And what do these mandatory markings look like? They are the holding point signs — that's the runway designator in white on a red background — and the no entry signs. The critical operational rule: pilots are not to pass any mandatory marking unless specifically cleared by ATC. So a painted red-and-white holding point on the pavement carries exactly the same authority as the signpost version — you stop there until ATC clears you. Then we have the information markings. These are the surface-painted replacements for information signs. Where an information sign would normally be installed but it's physically impracticable, the information is displayed on the pavement surface. And where operationally required, an information sign should be supplemented by information markings — so sometimes you get both, the sign and the painted version reinforcing each other. Now the placement and the colour rules are precise. The markings are displayed across the surface of the taxiway or apron where necessary, and positioned so as to be legible from the cockpit of an approaching aircraft — that's the design driver, the pilot's eye position. The colour coding is where you need to be careful. An information marking consists of an inscription in yellow when it replaces or supplements a location sign. And an inscription in black when it replaces or supplements a direction or destination sign. So yellow = location, black = direction or destination. But there's a contrast rule on top of that. Where there's insufficient contrast between the marking and the pavement surface — say the pavement is light and the inscription is yellow — then the marking must include a black background where the inscriptions are yellow, and a yellow background where the inscriptions are black. So you always guarantee the inscription stands out against the pavement. Finally, the markings are combinations of characters and symbols. And one specific rule: markings containing numbers only are only used for runways and runway designators. So a purely numeric marking — no letters, no symbols — is reserved exclusively for runways and their designators. That keeps the numeric-only markings unambiguous. So to tie it together: road holding markings guard road entrances to runways under local road law; mandatory instruction markings are painted holding points and no-entry signs you must not cross without ATC clearance; and information markings are painted location, direction, or destination information, colour-coded yellow or black with contrasting backgrounds, positioned for cockpit legibility, and numeric-only markings are reserved for runways and runway designators.