• Rijuta Dighe

The Cost of Bad UX Design

There are mistakes, then there are big mistakes, and then there are mistakes that change the course of history. In my previous blog, I had written how user experience design is something that affects us everyday. Mistakes in designing products cause small annoyances which we generally ignore! But what happens when these mistakes are made by professionals on large scale projects? What happens when user research is ignored on big engineering projects?

It causes loss of millions of dollars, people getting fired, recalling of products, loss of livelihoods, or even worse, fatal accidents!


"You've got to start with the customer experience and work back toward the technology, and not the other way round" - Steve Jobs


Here are 3 examples wherein poorly designed user interface caused historic disasters.

The Three Mile Island Accident (1979, Pennsylvania, U.S.A)

Background: The three mile island was a nuclear power plant on Three Mile Island in Pennsylvania, U.S.A. It had two separate units, TMI-1 (owned by Exelon Generation) and TMI-2 (owned by FirstEnergy Corp). On March 28, 1979, TMI-2 suffered a partial meltdown, which has been dubbed as 'the most significant accident in United States commercial nuclear energy.'

Loss: Fortunately, no deaths or accidents were reported, nor were there any resultant cancer cases. But the cleanup that started in August 1979, ended in 1993 (after 14 years!) and the estimated cost for the cleanup is about $1 billion ($1,000,000,000). According to the United States NRC, 2.3 million gallons of wastewater had been removed.

The Accident: The initial cause of the accident happened eleven hours earlier, during an attempt by operators to fix a blockage in one of the eight condensate polishers (A condensate polisher is a device used to filter water condensed from steam as part of the steam cycle). Blockages are common in these filters and are cleaned by forcing the stuck resin out with compressed air. This did not succeed and hence he operators decided to blow the compressed air into the water and let the force of the water clear the resin. When they forced the resin out, a small amount of water forced its way past a valve which was stuck in open position and found its way into an instrument air line which caused the turbine to trip (emergency shutdown of power generating turbine). This caused large amounts of nuclear coolant to escape.

Usability Problems: However, the operators did NOT make any attempts to close the valve! Why? There was a whole team of design engineers (including the legendary Don Norman himself) investigating just that for months. Despite the critical valve being stuck open, a status indicator on the control panel seemed to indicate that the valve was closed. But in reality, the status light did not even indicate whether the valve was open or closed, but only whether it was powered or not! The status indicator thus gave false evidence of a closed valve, and when the control room operators were unable to interpret the meaning of the light correctly, they could not correctly diagnose the problem for several hours. By this time, major damage had occurred.

Author/Copyright holder: John G. Kemeny. Copyright terms and license: Public Domain

The control room where badly designed buttons and labels caused nothing less than a nuclear accident. Here, President Jimmy Carter is touring the Three Mile Island 2 (TMI-2) control room on April 1st, 1979.


Indeed, the control room couldn't have been more confusing than this.

A simple ON/OFF button and a status indicator can potentially cause a nuclear catastrophe putting lives in danger as well as causing million dollar damages!


The USS Vincennes Shot Down a Civilian Plane Because of Bad Cursors (1988)

Background: One of the most tragic events of 1988 war, was when US missile accidently shot down an Iranian passenger airplane in 1988. USS Vincennes (CG-49) was a Ticonderoga-class guided missile cruiser outfitted with the Aegis combat system and was used by United States Navy.

Loss: All 290 onboard the passenger airplane were killed immediately.

Usability Problems: The computer screen showed all the objects detected by radar in a given vicinity, and if the operator clicked on a particular object, the system would track that object. But if the operator wanted more information about that object, in this case, listening to radio signals, the operator had to move a separate cursor and click on the object again. Think of it like; suppose your computer had more than one mouse, you have to remember which commands are carried out by which mouse! Moreover, the cursor on screen looks exactly the same for both the mouse. So the operator in this case, was tracking one airplane (airplane full of innocent people) and listening to signals from totally different airplane (fighter plane parked several miles away).

Obviously, this reason would not be enough to shoot down the plane, they also had to think if the plane was moving closer like an enemy aircraft. But instead of telling the operator if the airplane was ascending or descending, the system just showed them the present altitude on a smaller monitor. The operator had to write down or memorize the altitude, wait a few seconds, then ask again and mentally compare the two results to see if the aircraft was going up or going down. Unfortunately, this led to a calculation error, and the operator reported the aircraft to be descending toward USS Vincennes, like an enemy aircraft would.

Inside the control room of USS Vincennes


Sometimes bad UX can be deadly!


Air Inter Flight 148 Crashed because of a small display screen (1992)

Background: On January 20, 1992, Air Inter Flight 148 crashed into the Vosges Mountains while approaching Strasbourg Airport in Strasbourg, France.

Loss: 87 out of the 96 crew members onboard were killed.

Usability Problems: Why on earth was the airplane heading towards the mountains, in the first place? A two year long investigation revealed that it was due to bad UX design of airplane screens!

The pilots had to enter the altitude on one screen and the metrics of that altitude on another. For example, you enter "5" on your microwave, and then you have another button to specify if it is 5 seconds, 5 minutes or 5 hours! Or for those of you familiar with photoshop, when you need to enter the canvas size, you enter "300" in one box metrics could be any from pixels to cm, or inches or whatever.

In this case, the pilots intended to put the plane on -3.3 degrees, which would have put them at a descend rate of 800 ft/min. So they entered -3.3 and set the plane on autopilot mode. Unfortunately, the plane was set at ft/mins instead of degrees. So, the system interpreted it as -3300 ft/min, which is almost over 4 times the intended speed. The small display screen could only show two digits, which is why it displayed only '33' as it was intended to be. Basically, the entire thing could have been avoided either with a better intuitive interface or at least a bigger display screen!

"It is easy to blame something as a human error, rather that is what most people do. But when every person is likely to make the same mistake, it is a major DESIGN FLAW" - Don Norman
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