The brain processes certain shapes and colours faster, Runway Incursion Prevention

Introduction

The heart of the airport is the vast movement area extending before and including the runway, along the taxiways and onto the apron. Surface Markings are provided on aerodromes. To assist pilots in identifying certain locations and to provide guidance for ground movement by day, visual navigation aids are provided, the standard for which is given in the International Civil Aviation Organization (ICAO) Annex-14.  New aircraft models, increased aircraft operations, operations in lower visibilities and technological advances in airport equipment combined make the ground environment at an airport one of the most challenging phases of a flight. There have been several instances wherein the visual aids have been misidentified or completely missed out by both pilots. There are plenty of examples of aircraft landing on a closed runway or a taxiway, entering a wrong taxiway or a runway incursion. This highlights the human factor aspect, where, under certain circumstances, humans cannot process the information provided by these visual aids for navigation. In this paper, we will analyze the cognitive aspect of shapes and colours or the signs that are used to make the visual aids and if they could be improved to enhance safety.

Information processing

A problem faced by all mobile organisms is how to search their environment for resources (Goldstone & Ashpole, 2004). The concept of a cognitive function helps analyze how people and information-intensive systems may interact (Boy, 2000). The task of a pilot is to achieve an objective. The controller obtains this endeavour, giving the aircraft a route to travel on the airfield. Guidance signs along the way help the pilot stay on course with their plan. The processing occurring in the pilot’s head involves both the left and right brain hemispheres working separately on their selected bits of information. They come together by combining the data to attain a universal understanding. Each half of the brain has its own hemispherical specialization. The left brain deals with logic and word meaning. The right brain manages symbols and abstract concepts. This processing is done in nanoseconds so that a guidance sign’s meaning is realised almost instantaneously. The brain is kept busy absorbing the intricacies of sign elements with the various combinations of letters, numbers, symbols, and colour coding.

Semiotics

Humans are driven by the desire to make meanings and thus cannot avoid interpreting things, and, in doing so, humans treat them as ‘signs’. Signs take the form of words, images, sounds, odour, flavour, action, events, objects, and so on, but these have no intrinsic meaning and become signs only when we invest them with meaning. Anything can become a sign if someone interprets it as ‘signifying’ something. Semiotics is an investigation into how meaning is created and how meaning is communicated. Its origins lie in the academic study of how signs and symbols (visual and linguistic) create meaning. Everyone is a semiotician because everyone is constantly unconsciously interpreting the meaning of signs around them – from traffic lights to colours of flags, the shapes of cars, the architecture of buildings, and the design of packaging. The term Geosemiotics comes from Scollon and Scollon (2003), who write that geosemiotics ‘refers to the real, physical, material world in which we live our lives’. In other words, the definition of geosemiotics is the meaning of signs in the environment/space according to their placement.

Traffic

Visual semiotics is immediately comprehensible through a codification of the choice of colours, size and shapes. In road traffic regulation, the key role is influencing any driver to prevent accidents correctly. Consequently, any information given by road signs should immediately strike the mind and impose good road traffic behaviour. Due in part to monetary limitations, automotive clubs were responsible for developing and disseminating the first traffic signs. Members would post signs, warnings, and notes to fellow motorists at various points on early roadways. Not surprisingly, since there was no clear design or location standard, there were many inconsistencies and safety concerns. In fact, according to the New York Times, a pioneering text responsible for introducing the notion of traffic signage was Reforming Our Street Traffic Urgently Needed, written for a magazine called Rider and Driver. The author’s simple plea included placing stoppage signs at intersecting roadways. This request came at a period in history where most roads were unkempt gravel or dirt, had no line markings, no standard travel speed, no designation between pedestrian and motorist areas, and no traffic lights (it wouldn’t be until 1914 that American Traffic Signal Company installed the United States’ first traffic light in Cleveland, Ohio.

Infinitely Idiotic: The Rationale for Shape

A key issue the Bureau of Public Roads faced was that many American motorists were relatively illiterate (U.S. Department of Transportation). This meant traffic signs had to be designed in universally understood ways, with or without the use of English words. Factors such as shape, size, and colour were particularly important in these formative years of traffic sign design. Over time, however, with increased automotive production efficiency (i.e., assembly line) and material consistency, the automobile became a financially viable option for many households by the early 1920s. Indeed, the Bureau of Public Roads recognized this rise in automobile popularity and sought a solution to the growing safety issues. Engineers toyed with various STOP sign shapes. Based on little more than intuition and some feedback from railroad engineers, the Mississippi Valley Association of State Highway Departments decided that the number of sides a sign has would indicate its “danger level”. These engineering types perceived that it was common knowledge that the circle had the most sides — an infinite number. Thereafter, circular traffic signs denoted areas with the highest level of danger for motorists. Take a moment to appreciate the lunacy of that decision. Over time, railway settings used exclusively circular signs. Whereas the octagonal shape of the STOP sign remained rooted in motorway settings.

The Rationale for Color

With the shape issue “resolved”, STOP sign designers then considered colour. Surely, red was the frontrunner. Alas, the Bureau of Public Roads began production of yellow STOP signs in 1915 in major automotive regions such as Detroit, Michigan (Moeur, 2010; http://www.trafficsign.us/yellowstop.html). Why yellow? Pioneering research in early Human Factors and physiology had revealed that the human eye was most efficient at detecting colours within the yellow and green spectrum, especially when scotopic vision (i.e., high use of rods, low use of cones) is used in low light (e.g., dusk; night time). Despite common belief, red is not easily or quickly detected in low light conditions. In fact, the colour red is almost impossible to discern at night without the assistance of an artificial light source (e.g., backlighting, headlights).

By 1924, all “warning”-type signs were produced in a standardized, bright yellow colour. Likewise, all other signs were given a white background to differentiate the two categories of traffic signs: warning and informational. Both of these lighter colours provided the best degree of contrast (with black letters) in conditions with low light (e.g., nighttime, rain, fog) that manufacturing methods could produce at that time.

Yet problems persisted

Despite their best efforts, the number of accidents and issues on the (deteriorating) roadways continued to increase from one year to the next. There were three central factors to this issue: a.) automobiles were being designed with greater power and speed potential; b.) more and more motorists were on the road; and c.) headlamps and streetlights were not efficient enough to illuminate STOP signs on their own. Headlamps at that time only offered about 100 ft. of illuminated distance in front of the automobile. However, today we know that your average (undistracted, unfatigued) motorist travelling at 30 MPH requires approximately 115 ft. – 187 ft. of stopping distance, considering average brake reaction times. As a result, there wasn’t enough distance for them to react to an unfamiliar or unexpected STOP sign and respond appropriately if motorists travelled any faster than 30 MPH.

The need at this point in the evolution of the STOP sign design was to enhance its visibility and luminance.

Extending Our Sight

Experts considered multiple design strategies. The one that initially won during the 1930s was the incorporation of glass “beads” into traffic signs. Glass beads less than 1 inch in diameter were glued along the sign’s perimeter and the word STOP. These beads incorporated diffuse reflection, enhancing visibility at night when the motorist’s headlamps were on. Unlike mirror reflection, diffuse reflection operates by “taking in” a light source and simultaneously distributing a portion of that light in all directions. For example, the same way that a car’s paint reflects the sunlight during the day. The net effect of a diffuse reflective STOP sign was that it enhanced visibility by (about) an additional 50 ft. – 100 ft. at night. However, the downside to this design approach was that it was inherently costly and time-consuming to produce. Reducing the cost and production time was a challenge.

By the late 1930s

Material scientists at 3M introduced a revolutionary retroreflective sheeting material that changed the STOP sign forever. Unlike the diffuse reflective beads, the retroreflective surface worked by “taking in” a light source and reflecting a portion directly back.

3M’s design, revolutionary as it was, wasn’t all that different from the glass bead approach. Like previous designs, they, too, used glass beads. However, the key difference was opting to crush the glass beads down to a slightly larger than sand-sized level. Afterwards, the crushed glass material used resin to adhere to the entire face of the STOP sign. This design approach worked — for a few years. Yes, it enhanced the STOP sign’s visibility compared to the glass bead approach. And yes, it was (a little) cheaper to produce. However, the rough surface of the STOP signs quickly collected dust, dirt, and debris. Over time, STOP signs took on a dirty, dull appearance, reducing their visibility to some extent. Likewise, moisture would cling to the STOP sign’s surface during inclement weather, making it challenging to read. The issue was resolved within a few years by covering the STOP sign with a transparent, smooth film. This solution offered the best of both worlds: transparency, which allowed the STOP sign to retain all of its retroreflective properties, and the smooth surface eliminated the accumulation of dirt and moisture. The industry refers to this type of sheeting as “flat-top sheeting” — also known as “engineering grade sheeting”. It offers an enhanced viewing distance of up to 500 ft. for motorists. Engineering grade sheeting is still in production and used in environments with light traffic and lower speeds.

Seeing Red

To recap: 1940 – 1950s, all new STOP signs produced for use in the United States had the following properties:

• Octagonal shape
• Yellow background color
• Black “stop” text
• Black border (inlaid slightly from the perimeter)
• Retroreflective material (viewable up to 500 ft.)

So, when (and why) did the STOP sign turn red? In 1954, a big decision was made about traffic signs. Many signs on the roadways were yellow. As described earlier, yellow traffic signs indicate some form of warning or caution to motorists. But there are tons of things that motorists have to be cautious of while driving. For example, “SLOW”, pedestrian crossing, traffic light ahead, “DIP”, “NO OUTLET”, “STREET CLOSED”, “DEAD END”, deer crossing, construction ahead, etc.… Bear in mind the list of traffic signs was much, much shorter in the 1950s than it is today, but you get the point. Dozens of signs. All yellow. All black text. It gets confusing. Confusion on the roadway is a precursor for accidents.

The STOP sign seemed to become red almost overnight. According to revisions made to the Manual on Uniform Traffic Control Devices in 1954, the STOP sign should be “red” with “white letters”, which followed similar practices and colour-coding systems adopted by traffic signals and railroads. According to a New York Times interview with Professor Gene Hawkins from Texas A&M University, “red” has always been associated with the idea of “stopping” (Greenbaum & Rubinstein, 2011: http://www.nytimes.com/2011/12/11/magazine/stop-sign.html?_r=0). After all, red had been used at traffic lights for the same purposes for nearly 40 years. Implicitly too, the colour red has strong associations with themes such as “danger”, “blood”, and “bad” — all things that potentially stem from choosing to run a STOP sign. But if this were the case, why didn’t the STOP sign switch over to red sooner? The issue was production. Yellow wears quite well in heavy traffic environments with rocks, sleet, sunlight, exhaust, and rain. On the other hand, Red degraded too quickly; signs would have had to be replaced (which adds to cost, time, etc.). Early red STOP signs are a testament to this issue. Even after guidance from the Manual of Uniform Traffic Control Devices, manufacturers still weren’t quite sure how to colour the sign in a red that would resist fading and slow but gradual wear. As a result, it would still be a couple more years until STOP sign manufacturers got the “recipe right” for the red colour they needed. To help you keep perspective on all of this — consider the following. These design iterations occurred almost a decade before many of today’s government agencies and organizations aimed at traffic control were firmly established. For instance, the National Highway Traffic Safety Administration (NHTSA) didn’t exist until 1970, when it was introduced as an offshoot of the Highway Safety Act. Yet even at this point in history, engineers, scientists, and motorists understood the need to promote safety on the roadway.

Modified Runway Holding

In 2002, the FAA and the industry teamed up to study and develop a modified runway holding position marking, which reduces the number of runway excursions. After a series of tests, two distinct options were available.

1. Modified centerline
2. Enhanced surface painted holding position

The effect of the modified centerline was to increase the distance at which the holding position was sighted. This was based on the pilot’s feedback that usually, pilots direct their attention towards the taxi centerline to keep the aircraft aligned. Any change in the taxi centerline would be noticed faster than other mitigating factors like signboards and points. Enhanced painted holding signs increase runway awareness both specifically and generally. The signs’ red colour generally increases runway awareness; pilots stated that the colour red would be immediately associated with the runway environment (red appears nowhere else on the taxiway surface). As the pilot gets closer, these signs also provide specific runway awareness. That is, pilots know not only that they are approaching a runway but also the runway’s identity and location. The whole was not the sum of its parts but a significant increase in awareness. The additive effect of two relatively weak signals was enough to overcome the detection threshold at distances farther than one relatively strong signal.

Visual working memory

The visual working memory plays an important role in the visual search process. VWM involves the use of both short term as well as long terms working memory. Optical acquisition of objects through attention results in storage of these images as separate files in the long-term memory. The short-term memory retains information for only a few seconds. The guidance sign which is searched is placed in the short-term memory, and only a few seconds are available for Brian to decide if there is a match. If an affiliation exists, the pilot goes to the next objective element on the taxi list. If there is no relationship, the visual clue is disregarded. VSTM is highly limited in its capacity: only four simple objects and six spatial location scans are retained (Olson& Jiang, 2004).  Chunking is a way to improve the performance. With object-based chunking, multiple items can be remembered as a single, complex pattern rather than as several isolated items. The VLTM may help the VSTM with this associative process to reinforce chunking. The FAA made the chunking process easier by mandating all airports code taxiways with an alphabetical or alphanumeric system. This shortened guidance signs legends to one or two-letter names. 

Sign reading

When reading a sign for a necessary runway hold, the runway threshold end’s matching number must be on the same side as the sign (see Figure 9). The left runway end will be displayed to the left of the sign, and the right runway end will be displayed to the right of the sign. Communication with the FAA tower could be confusing. When a pilot sees this indication, they have to mentally switch gears because this information display method needs to be ignored in favour of one that only uses some of the data.  The runway designator that is being used in the direction of landing or departure is all that the pilot uses. The sign provides more information than is necessary at any one time, yet the flexibility provided by the system accomplishes it with the fewest possible words. When confronted with this display, the pilot must adjust and choose the appropriate information section.

Runway incursions

A runway incursion is any occurrence on an airport runway involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in a loss of required separation with an aircraft taking off, landing, or intending to land. According to DGCA data, the number of runway incursions in 2018, 2019, 2020, 2021, and 2022 were 40, 25, 15, 35, and 45, respectively. Various factors contribute to runway incursions, including working memory decay, interruption, miscommunication, and disorientation, and there is a technological answer for each (Hooey & Foyle, 2001). Such technological solutions include special guidance on a heads-up display (T-NASA; Foyle et al., 2001), runway status lighting systems (Young, Wills, & Smith, 1996), enhanced markings and an emphasis on better training. 

The runway hold line above is the only mandatory painted element in the current marking system that warns pilots of an upcoming runway. However, some concerns are associated with it, among which is that its abstract symbology makes it difficult to remember which side is associated with the runway. Some pilots, particularly those with few flight hours or who do not fly regularly, have trouble remembering how the hold line is oriented. During evaluations, several pilots incorrectly associated the dashes with the taxiway side of the hold line. The surface-painted holding position signs increase runway awareness both specifically and generally. The signs’ red colour generally increases runway awareness; pilots stated that the colour red would be immediately associated with the runway environment (red appears nowhere else on the taxiway surface). As the pilot gets closer, these signs also provide specific runway awareness. That is, pilots know not only that they are approaching a runway but also the runway’s identity and location.

Rounded vs Sharp

Rounded corners are more effective for maps and diagrams because they allow our eyes to easily follow lines “as it suits better to the natural movement of the head and eyes respectively”. Sharp corners throw your eyes off the line’s path, so you end up experiencing abrupt pauses when the line changes direction. But with rounded corners, the line leads your eyes around each corner to continue along the path smoothly.

Which one is easier to follow? Rounded corners also make effective content containers. This is because rounded corners point inwards towards the centre of the rectangle. This puts the focus on the contents inside the rectangle. It also makes it easy to see which side belongs to which rectangle when two rectangles are next to each other. Sharp corners point outward, focusing less on the contents inside the rectangle. They also make it hard to tell which of the two sides belong to which rectangle when two rectangles are next to each other. This is because each rectangle side is exactly a straight line. The sides of a rounded rectangle are unique because the lines curve towards the rectangle to which they belong.

Conclusion

The data suggests that despite the use of enhanced surface markings at the runway holding point, pilots continue to fail to notice and process the warning signs. The shape and colour of the signs are the most important factors. While the runway ahead signs are rectangular shapes with pointed corners, painted in red and text written inside, as proved above, the edges need to be rounded. The colour yellow attracts more attention than red, and the human brain processes shapes faster than written text. Therefore, an ideal runway ahead sign should be a circle or a rectangle with rounded edges and painted yellow. Instead of a runway ahead, the sign of an aeroplane landing would better enhance the pilot’s situational awareness.