Runway Visual Range Is Runway-Specific, Not Airport-Wide Visibility
A Runway Visual Range (RVR) group in a METAR reports visibility information for a particular runway. Read from left to right, it identifies the runway, gives an instrument-reported distance, and may include a short-term trend. It does not replace the METAR’s prevailing-visibility figure for the airfield as a whole.
The distinction is visible in a National Weather Service example that reports prevailing visibility as 1400 and separately includes R04/P1500N and R22/P1500U. These are different report elements: the first gives the prevailing-visibility value, while the latter two describe RVR on runways 04 and 22. The runway-specific readings should not be substituted for the airfield’s prevailing-visibility figure simply because they appear later in the METAR string. [1]
That separation matters both when reading a METAR manually and when software parses one. Prevailing visibility describes conditions across the aerodrome; an RVR group supplies a runway-specific measurement. One value may help describe the conditions relevant to a particular runway, but it does not become a general visibility value for every part of the airport or every runway.
What the RVR group identifies
The initial R marks the group as runway visual range information. The runway designator immediately following it identifies which runway the value applies to. A group such as R04/P1500N therefore applies to runway 04, while R22/P1500U applies to runway 22. Where parallel runways need to be distinguished, L, C, and R designate left, center, and right. [1][2][3]
The group’s distance is not an alternative spelling of prevailing visibility. It is attached to the runway identifier, and its interpretation depends on that relationship. A reader who extracts only the number and ignores the runway designator loses essential context.
How to Parse the Group from Left to Right
An RVR group is easiest to interpret as a sequence: runway identifier, slash, distance or distance range, and—if reported—a trend letter. The exact details can vary by report and unit convention, so decode the characters that are present rather than assuming every group contains every possible component.
Runway designator and slash
In R04/P1500N, the first R introduces the RVR group and 04 identifies runway 04. The slash separates the runway designation from the measurement information. A parallel-runway suffix belongs to the runway identifier: for example, R27R/1100D identifies the right-hand runway 27, followed by the RVR value and trend. The suffix R in R27R means right; it is not the group’s initial RVR marker. [1][2]
Distance, units, and limit qualifiers
The digits after the slash give the reported RVR distance. The cited international examples use meters, while U.S. reports may use feet, sometimes marked FT. Always check the report’s format and units before comparing a value with another source or converting it for an application. A number without its units can be misread even if the runway and group structure have been recognized correctly. [2][3]
A leading P or M qualifies the distance as a limit rather than an exact value. P1500 means greater than 1,500 meters in the cited example; M0050 means less than 50 meters. Thus, R04/P1500N does not report an exact RVR of 1,500 meters. It reports a value above that threshold. [1][3]
Some groups show a variable range. In R24/0950V1100, the V separates two values: the reported RVR varies between 950 and 1,100 meters. The two numbers describe the range; they should not be mistaken for separate runway readings. [2]
Trend letters
A final U, D, or N describes the recent tendency: upward, downward, or no distinct tendency. For example, the NWS example interprets R22/P1500U as runway 22 RVR greater than 1,500 meters and rising. The German Weather Service specifies that the trend describes the preceding 10 minutes; it is a report of recent change, not a prediction of what will happen next. [1][3]
Read the trend only after identifying the runway and distance. U does not mean that the entire airport’s visibility is improving, and D does not say that every runway is deteriorating. The letter belongs to the particular RVR group in which it appears.
RVR and Prevailing Visibility: Related, Not Interchangeable
Both prevailing visibility and RVR describe visual range, but the METAR presents them as separate information.
The practical reading rule is therefore simple: retain the prevailing-visibility figure as the airfield-wide visibility element, and retain each RVR value with its runway identifier.
The NWS example, with 1400 alongside two runway groups, makes this distinction explicit. [1]
This also clarifies how to compare different METARs or different parts of one report. Before deciding that visibility has improved or worsened, check whether the values being compared refer to the same kind of measurement, the same units, and—when reading RVR—the same runway. Comparing a runway-specific RVR with prevailing visibility as if they were interchangeable can produce a false impression of what the report says.
For example, the following interpretation preserves the report’s structure:
| METAR element | Correct reading |
|---|---|
1400 |
Prevailing-visibility value reported separately for the airfield |
R04/P1500N |
Runway 04 RVR greater than 1,500 meters, with no significant change |
R22/P1500U |
Runway 22 RVR greater than 1,500 meters, with an upward trend |
The example demonstrates why it is unsafe to take the largest or last visibility-like number and treat it as the airport-wide value. The runway designator and the RVR prefix are part of the meaning, not decorative syntax. [1]
This distinction is relevant to data systems as well as human readers. A parser should store prevailing visibility separately from RVR groups, associate each RVR value with its runway, preserve limit markers such as P and M, and retain a reported trend as a trend rather than a forecast. This is a parsing discipline, not a claim that the METAR alone determines whether a particular operation is permitted.
VectorWX, at https://vectorwx.app, is a student-learning display for reading these groups side by side. As an independent example, the central design question for any such workflow is whether it preserves the original categories and associations in the report: one field for prevailing visibility and distinct runway-linked fields for RVR. The available sources establish the METAR decoding distinctions; they do not substantiate claims about specific VectorWX systems or measured error rates. [4]
Why the Distinction Matters as Weather Data Moves Through Systems
METARs are read by pilots, dispatchers, and software that may display, filter, or transform their contents. A compact coded string makes accurate field separation important: if a system treats an RVR number as a replacement for prevailing visibility, it has changed the meaning of the report rather than merely reformatting it.
A robust interpretation keeps four questions attached to each RVR group:
- Which runway does it describe? Read the runway designator immediately after the initial
R. - What distance is reported, and in which units? Do not compare values until units are clear.
- Is the value exact or bounded? Preserve
Pas greater than andMas less than. - Is there a trend or variable range? Read
Vas a range delimiter andU,D, orNas a recent tendency, not a forecast. [1][2][3]
Those checks help prevent two common misreadings: replacing the airfield’s prevailing visibility with an RVR value, and treating the final trend letter as a prediction. They also make runway-specific information easier to compare without stripping away the context that gives it meaning.
As METAR data is presented in dashboards and automated products, the underlying principle remains the same: preserve the distinction between report elements. A display may make values easier to scan, but it should not merge airport-wide prevailing visibility with one runway’s RVR. For a human reader, the equivalent habit is to decode the whole group before acting on any one number.