Ergonomics of Status Indicators: Signal & Warning Light
Visual Display
A visual display is a device that uses your eyes to provide information about things, events, or situations. Sometimes the display will be used in addition to information received by personally watching the event or scenario, but in certain cases, the display may be your sole source of information.
There are 2 types of Visual Display:
Quantitative displays: Quantitative displays provide precise information. Digital quantitative displays, such as the clock on your computer, provide information directly as numbers. Analogue quantitative displays can also be utilized in situations where a length or angle represents the information, such as a thermometer in which the length of mercury or alcohol represents the temperature.
Qualitative Displays: Qualitative displays provide information about specific conditions, such as hot or cold, alert or no alarm. These displays can show the rate of change or the direction of departure from a target value. The specific value is not needed, although that may be conveyed to you by other, quantitative visual displays. Indicators and warning devices may be included in these displays.
Status Indicators
Sometimes qualitative information indicates the status of a system or a component, such as the use of some displays for a check reading to determine if a condition is a normal or abnormal. Lights, such as traffic lights, are the most basic and widely used status indicators. Although many status indicators are lights, alternative coding schemes, such as the controls on certain stoves that are labelled to indicate the off position, can be employed.
Signal and Warning Lights
Flashing or steady-state lights are used for a variety of things, including warning signals, nighttime aircraft identification, navigational aids. Warning displays draw your attention and demand you to take action; for example, a red traffic signal requires you to stop your car.
There are several aspects to consider when designing signal and warning lights. Such information is briefly detailed further down.
Viewing Range: The reading distance for screens is generally 300–750mm. The most prominent display viewing distance should be determined by the size of details shown on a display. Indicators should be within 30 degrees of operator’s normal sight of view.
Luminance, Exposure Time, Size: The absolute threshold for detecting a flash of light is determined in part by the size, brightness, and exposure duration. The lower the luminance required to detect the light 50% of the time, the larger the light and/or the longer the exposure time.
Flash Rate of Lights: In the case of flashing lights, the flash rate should be significantly lower than the rate at which a flashing light appears as a steady light (the flicker-fusion frequency), which is about 30 times per second. Flash rates of 3 to 10 per second have been advised for grabbing attention in this respect.
Color of Lights: Color is another factor that influences the effectiveness of signal lights. The researchers discovered that background color and ambient lighting can interact to affect people’s ability to recognize and respond to different colored lights. However, with low signal-to-background brightness contrast, a red signal clearly outperforms green, yellow, and white, in that order.
Example
What flash rate should you keep? Flash rates should be from about 3 to 10 per second with equal intervals of light and dark.
What should be light intensity? The light should be at least twice as bright as the immediate background.
What should be light color? Warning lights are normally red because red means danger to most people.
Thank you!
https://www.ergonomics4schools.com/lzone/displays.htm
https://ergo.human.cornell.edu/DEA3250Flipbook/DEA3250notes/dyndisplay.html
https://ocw.upj.ac.id/files/Slide-PRD514-PRD514-Slide-4.pptx
