Road sign “Objects, obstacles or parts (fallen) on the road”

Objects, obstacles or parts on the road: A road sign proposed for VMS, it’s long development, and a method to improve LED signs.

Proposing a road sign for LED-Variable Message Signs (VMS), and explaining its development that lasted from 2006 to 2021. It exemplifies an improved way to design road signs to be shown on LED displays.

→ Dieser Text ist auch in Deutscher Sprache abrufbar.

As there was demand for a warning from danger caused by a variety of objects fallen on a road’s surface, EU Research project SOMS/In-Safety took on the task to – alongside many other signs for road use – create an appropriate symbol to be used on Variable Message Signs equipped with Light Emitting Diodes (LED).

To do so, iterations of designs for such a symbol, alongside repeated testing for the degree to which they were understood (comprehended) were carried out. While design was governed by a novel method allowing to increase the visual (viewing) distance for VMS and regular road signs simultaneously, testing was performed by adhering to evaluation of comprehension according to ISO 9186:2001, done in three countries.

Variant A and B of Referent 2.3.11

For example, symbol ‚A’ (No. 2.3.11) scored at 14.2 (out of 100) in the first comprehension test. Due to low performance, the image was revised and tested again (2.3.11, B, 2nd Comprehension Test), with a score of 66 (out of 100).

This above-average result is still an improvement to the generic danger warning sign A, 32 of the United Nation’s Convention on Road Signs and Signals, which needs an additional panel underneath specifying the actual danger in local language (e.g. „Objects“, etc.). As the exclamation mark in sign A, 32 does not give any visual clue on the type of danger, understanding of the sign is impossible for those wo do not speak the local language.

A long hiatus, new information and new requirements

Accordingly, for 12 years, variant B remained the symbol proposed for application until 2021. At that time ASFiNAG contracted the Author to develop numerous road signs for use on VMS, using updated knowledge on visual design and viewing distance from a study performed in 2019 on the premises and equipment of swarco Futurit.

A prerequisite of the project was that danger warning signs on VMS in Austria had to include the red triangular border. Due to this, only little space (and therefore, rather few LED-elements) remained within that border to display symbol variant B. As a result, the image could not maintain the distances between active (lit) LEDs required to be visually discriminable over greater viewing distances. In effect, the symbol was perceived as showing evenly sized and evenly distributed elements, with no obvious image content.

Accordingly, the symbol’s image content had to be simplified, which meant starting again from scratch.

Developing a suitable symbol with components already in use

An advantage of road signs is, unlike other graphical communication systems using symbols, that they are learned in driving school. This way, its components are readily understood, and they can be less pictorial and less complex. So there is an opportunity for a simpler symbol for sign ‚objects, obstacles or parts (fallen) on the road’ that is capable to fit into the triangular red border while remaining visually discriminable.

Many road signs provide indications on their meaning through visual clues, making it easier to learn and remember them. A, 7 „uneven road“ uses variations of a horizontal bar at the bottom of the space within the red triangular border to refer to several conditions of road surface. This principle has been applied to the new image content of ‚objects, obstacles or parts on the road’.

As in A, 11a „falling rocks’ (see below), objects falling or have fallen on the road are represented in mid-air, without vertical „action lines“ known from comic book drawings. And to differentiate from the amorphous stones of A, 11a, a crate as found in symbol W015 „Warning; Overhead load“ of international Standard ISO 7010 „Safety colors and safety signs“ was chosen to represent „objects“, „obstacles“ or „parts“.

The result

With the two graphical components put together, the sign’s appearance is unique and can not be confused with any other road sign. Its renderings for several prescribed dimensions (as legally required by Austrian law) are clearly discriminable. These 4 ready-for-use renderings are available for FREE, here: TS0330LED.

Recommendations for use:

Please note that the digital files to be displayed on LED-matrices were created using an anti-aliasing function, which helps to counter the graphical components displayed by LEDs to blur, merge and therefore become less discriminable (see study from 2019). Consequently, an LED display device itself does not require to support an anti-aliasing function.

Further more, throughout the first 10 years of its use, it is recommended to add the terms „objects“, „obstacles“ or „parts“ in local language to the sign to support understanding of the meaning during the introduction phase. After that, the use of the chosen term should be discontinued.


The new symbol to be used for the danger warning sign of „Objects, obstacles, or parts falling/fallen on the carriageway or road)“ provides the required visual clues to be learned, recognised and acted upon, while it remains clearly visible and distinguishable from other signs even at small scale depiction.

The insights gathered in a study in 2019 on creating sign-depictions for LED-display devices used to elaborate this sign allows to determine and ensure visual discriminability in relation to driving speed/viewing distance. The use of the anti-aliasing function in sign design is recomended.