Driving at night is a dazzling experience. Is that because headlights are maladjusted, or too powerful, or not dipped? Jasper.
All three of those reasons are common. All inflict discomfort and risk on every road user. Three other key ingredients are the poor quality of road markings, failure to segregate vehicle lanes from non-illuminated pedestrians, animals etc., and - less widely recognised - the age of drivers.
The human eye is very good at adjusting to different levels of illumination. The muscles of the retina make the pupil open or contract, by an optimal amount, almost instantly. Until you are about 45 years old (the design life of human evolution). Thereafter, in most people this muscular reaction progressively slows down, so older eyes don’t prevent dazzle so promptly and don’t recover from it as quickly.
Standard car headlights do not have 55-watt beam elements and 45-watt dip elements because some auto electrician thought those numbers sounded nice. The 45-watt dip is a carefully judged balance between the volume of light that will allow you to see well without depriving oncoming drivers of the same privilege.
At that level, with properly adjusted angles of light (slightly below horizontal and slightly to the left) drivers heading in opposite directions both have a fair chance of seeing where they are going. (Car technology changes, but the human eye hasn’t).
Headlight technology has advanced quite a lot, but the principle still applies that if one driver has more powerful (or maladjusted) lights, the other drivers are dazzled; if a dazzled one responds by flicking the “beam” switch or in the longer term also fitting more powerful lights, both drivers are blinded.
Hence, if everybody has lights of the right brightness, properly adjusted, everybody can see. If anybody fits brighter lights, then others will fit brighter lights, and pretty soon everybody will have brighter lights, and nobody will be able to see.
So, unless you believe that, for some reason, you and you alone should have brighter lights than everybody else, fitting a more powerful bulb in your headlights is antisocial and should be illegal behaviour.
Given the unreliable marking, lighting and surface condition of Kenya’s roads, even beam headlights do not provide sufficient illumination for motoring at high speed at night.
At over 100 kph, you’re relying more on optimism than on optics. If you want to go quicker than that, you should still not fit more powerful headlight bulbs - you should fit auxiliary driving lights (aka spotlights) and use them only when there is nothing in front of you, either approaching or going the same way.
And if there is no such empty road on your journey, drive at a speed that allows you to see clearly enough on dip. You should be able to bring your car to a halt (!) within the distance you can clearly see ahead. That is the law.
Strictly speaking (and this is law as well as logic), spotlights should be wired so they cannot illuminate when the standard headlights are dipped, even by mistake. They should have an independent switch that can turn them off completely, or on only in conjunction with beam headlights.
Given that simple logic, dual filament headlight bulbs (that is, bulbs specifically designed for standard headlight switches and fittings), it is astonishing that bulbs of paint-blistering wattage are readily available in auto shops.
Many offer a holocaust of quartz-halogen horrors. A diabolical 100-watt dip/120-watt beam combination is the first (!) option they will offer when you ask for a dual filament bulb. No wonder driving at night in Nairobi is like being a flea caught in a pinball machine. This is supposed to be driving, not a discotheque.
Already, we know there is much to be done in driver education about the proper use of dipped and beam headlights. There is much to be done on maintenance and roadworthiness standards for the proper adjustment of headlights so that those dips and beams work on both sides and point in the right direction.
But even if we somehow achieve those two miracles, it won’t help if cars are being fitted with armour-piercing dip filaments. Laugh on, cowboys, but in head-on collisions, both drivers die.
