Driving the very pleasant Citroen C5 home last night, I got to thinking about the importance of the instrument binnacle, my thoughts directed that way by the unusual manner in which the Citroens needles are displayed.

Floating dials - nice, but maybe missing a point?

The pointer actually appears to be affixed to the outer edge of the instruments, so there’s no central point from which the needle sprouts. It’s quirky and works well enough, when you’re just pottering around town, but when you’re really driving hard (in an entry-level, 2.0-litre diesel C5 you ask? What can I say…) the shortcomings of deviating from the accepted norm can become a bit annoying.

It is an automatic as well, so it’s not like you really need to know what revs you’re at, but still. The problem comes down to the raw mechanics of the human biology you see. When you’re running flat out, your eyes are focussed as far off into the distance as possible basically. For the muscles controlling the various focussing functions of the iris, there has to of necessity be a minute amount of time allowed so that they can do their thing when you rapidly switch that focus.

So, when you flick your eyeballs down to the dials for an instant update on the position of the engine’s revs and the speed you’re travelling at, you don’t actually have the time at very high velocities to wait for the mecahnics of this refocussing to happen. So your gaze spears straight to the central point of the tacho, which in this case just isn’t there, so that you can at least get an indication, within a few hundred rpm, from just the base of the needle being even remotely in focus.

Now to scan the outer ring of that same dial for a well-lit but nevertheless small pointer, at the very least doubles the amount of time your eyes are off the road. It also then doubles the amount of time they have to refocus on that far-distant point where the road disappears over the horizon, although this is less of a bother really.

When I first noticed this oddity, I figured acclimatisation to the way in which these dials actually operate would dispel the problem…

But it won’t. The tiny, complex, and astonishingly smart little muscles in your eyes just will not work any faster than that, period.

This is  no criticism of the C5, or any vehicle which uses some lateral thinking in the development of their instrument pack. Just a bit of an insight into why enthusiasts often kick against these kinds of seemingly insignificant changes to everyday functions of the physical task of driving. Often the old ways, although perhaps not the prettiest, have been based on years of research into the operation of us, the operators, engineered to be the most compatible with these methods, and implemented as an engineering item rather than a design feature.

When it comes to the life and death act of driving a car, little almost natural advantages like that are quite important.