Redundancy is the use of excessive elements to prevent a system failure. Multiple elements are used to maintain and increase the reliability of the system in case of a failure of an element within the system. There are 4 different types of redundancy: diverse, homogenous, active, and passive. Diverse redundancy is when different types of elements are used to prevent a single form of failure. Homogenous redundancy is the use of multiple elements of the same type, but is susceptible to single cause of failure. Active redundancy guards against both system and element failure with the use of redundant elements at all times. Passive redundancy is when an active element fails and is replaced, ideally used for noncritical elements.
SOURCE:
Lidwell, William. “Aesthetic-Usability Effect” Universal Principles of Design: 125 Ways to Enhance Usability, Influence Perception, Increase Appeal, Make Better Design Decisions, and Teach through Design, Rockport, 2010.
Source Example:
Super Cow
Many redundant elements were used to make sure the Super Cow would be able to withstand a Hurricane with no failure.
Non-Source Example:
Golden Gate Bridge
PhotoSource: sftravel.com
Suspension cables are a form of redundancy.
Real Life Example:
Pillars
The golden gate bridge is an excellent example of redundancy. Another great example for redundancy is automotive crash-safety engineering. When creating systems for crash-safety, manufacturers provide several levels of redundancy. It is clear why, we all want to know that if for some reason ten things fail, there is an eleventh feature that may save our lives. For example, cars consist of the crumple zone consisting of the safety belt, airbag, etc as the first line of safety. Couple this up with fuel injection which provides handling response when you suddenly see an oncoming impediment. Now companies use intelligent features to aid safety: automatic stopping and warning signals (using radar sensing for foresight), cameras that sense objects and give visibility in blind spots (blind-spot assist and rear-cam, for example). https://www.mbusa.com/mercedes/technology/videos/detail/title-safety/videoId-fc0835ab8d127410VgnVCM100000ccec1e35RCRD
Good description of the principle, Calvin! You did a good job of summarizing the strategy in a concise manner without sacrificing understanding; I liked how you provided detail into the four types of redundancy. All of them seem to serve one purpose which is prevent failure, which is critical in the examples you provided—in any situation where failure could result in life or death or compromise in safety and security, redundancy becomes a very necessary strategy to implement.
For example, many modern buildings have an emergency power system that kicks in if the regular power system fails. The more important the work taking place inside the building (say a hospital), the more likely the building will have one or more redundant power sources.
That said, are there any circumstances in which redundancy, in any of the four forms you’ve outlined, unnecessary? When it comes to engineering, it’s critical. But in design for digital interfaces and experiences, in what ways does redundancy serve the user or get in the way? Perhaps additional ways to communicate the same message can increase the odds the message is received by your audience. Redundant systems of navigation can help visitors find their way on a website. Redundant means for completing the task can help your audience achieve their and your goals. In what ways is redundancy in human computer interaction and design a benefit or a cost?
I liked your example of bridges as showing redundancy to avoid collapse of the bridge. Its interesting that sometimes, we actually want redundancy, just so make sure nothing goes off or wrong. An example that comes to mind is photographers who take multiple pictures of the same shot. They may change exposure/timing, but they take multiple shots of the same thing, just to make sure one of them comes out right.