Reflections on Reflections


Reflections on design errors in the human machine interface

Having recently bought a new car I was driving home and noticed that the illuminated lighting controls were reflected in the right hand wing mirror. See the picture below for the effect. These sort of reflections are at best annoying, but in the worst case they could mask the lights of a car in the right hand lane and lead to a side swipe during lane changing.

This is one of those classic crew systems design errors, well understood in domains such as the aerospace field (1). Not so much in the car industry apparently.

But what really interests me is the fractured nature of engineering knowledge this problem illustrates. I guess there is an implicit assumption we make that “we’re all getting smarter”, but if that’s the case why are the same ‘known’ errors commited over and over again?

Henry Petroski (2008) points to a study by Silby (1977) of bridge failures that shows a 30 year period between major bridge collapese and posits that in any technology we go through a cycle of learning, mastery, overconfidence and subsequent failure due to over reach.

Myself I’d point more to the fragility of corporate memory within organisations and design teams. In an environment of rapid organisational change it’s extremely hard to provide mentoring and oversight of young engineers, who unfortunately, don’t know what they don’t know.

This remorseless cycle of destruction is exacerbated by the deficiency of many codes and standards that specify the ‘what’ that must be done from a compliance standpoint, but not the why. And without the reason for compliance there is always the temptation…

I do however agree with Petroski that failure breeds reflection, insight and knowledege and that engineers (especially young engineers) need in may ways to experience failure themselves or learn through the failures of others.


1. Where evaluations of cockpit transparencies for reflections are required as part of the development of a new aircraft.

These effects are particularly a problem for fighter aircraft with a large curved canopies where the pilot displays sit comparatively close to the canopy. See a paper I wrote on the challengers of integrating NVIS into a fighter cockpit here.


1. Petroski, H. Success through failure: The paradox of design, Princton Press, 2008.

2. Sibly, P.G., Walker, A.C., Structural Accidents and their Causes. In: Proc. Inst. Civil Engineers. 62 (May 1977), pp. 191–208 part 1. 1977.


Reflected indicators

Right hand instrument console indicators reflected in side mirror and centre console reflected in side window

And a daytime view of the right hand instrument panel and mirror