Safe Speed Forums

I found this on a forum some years ago:

To those interested in possible EU banning of night driving by the elderly, I passed this to one of my sons who is a lighting researcher. His response follows.

There are two common pathologies which affect older drivers.

1. Macular Degeneration, which means that the most sensitive area of the retina (the fovea, used for detailed resolution) becomes progressively pigmented as the person ages, and becomes less sensitive to light. This happens pretty much uniformly among the population (ie only small variations among individuals, normal 20-year olds do not have it), in much the same way as hearing loss. The effect of macular degeneration is that higher illumination levels on the roadway are required. Existing recommendations already cover typical levels of macular degeneration in older drivers.

2. Crystallisation of the lens and cornea. This is less uniform across the population, although again it is associated with age and is not found in normal 20 year olds. The upshot of this is that incoming light is scattered across the retina, causing a "veiling luminance" ie a yellow-orange (in the case of sodium lights) tinge across the whole field of view which obscures objects such as obstructions on the carriageway. Increasing illumination on the roadway does not improve visual conditions for drivers with scattering problems - the only solution is to use low-glare lighting, i.e. high-pressure sodium or metal halide lamps in reflectors with a narrow beam (these lamps are physically smaller than low-pressure sodium and hence more photometrically controllable, this is why they are generally considered better, it's primarily a size issue not a spectrum issue).

The evidence proves very conclusively that although older drivers have consistently poorer vision than younger drivers, their visual skills are perfectly adequate. In some cases macular degeneration can result in the sufferer being registered blind, but is usually not so serious. Unless he or she has a diagnosed visual condition such as glaucoma, cataracts, diabetic retinopathy, a driver of any age is visually competent for the task. This area of research was resolved long ago and is no longer a subject of debate, and there's certainly no basis for blanket disqualification of drivers over 65. Although given the prevalence of visual conditions in these drivers, it would be prudent to require eye tests every couple of years.

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http://www.itsyourduty.org.uk

Sorry to go off on a tangent a bit, but so I can learn from more experienced drivers, could you give me a couple of examples of when you have had to do this, or at least hypothetical examples of when you would do this.

I can think of three within the last few years.

* A shadow ahead that might have been a pedestrian, but turned out to be nothing more than a shadow.

* An unlit car that pulled out of a side road ahead. I don't know what I saw before I flicked the mainbeams on, but there it was and I had plenty of time to slow down.

* Sudden uncertainty about "where the road goes" in a set of roadworks. They have put up cones and keep left signs, but the keep left signs are wrong. I have to pass to the right of them. I need the extra light to understand this.

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Paul Smith
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The Safe Speed campaign demands a return to intelligent road safety