So what to do, other than going really slowly? The effective way to significantly improve that safety margin is fitting driving lights or spotlights that pick out details far beyond what most good high beams can manage.
Driving lights are designed to provide a long-range, reasonably wide beam, probably "spilling" some light to the side to help illuminate the edge of the road. A spotlight is just that - a narrow cylinder of light that reaches deeply into the night like a mini military searchlight.
Although spots might seem like the ideal long-range night driving assist, a pair of spotlights aren't as useful as a pair of driving lights, or one driving light paired with a spot.
Spotlights and driving lights must be wired so that they can only be used with the vehicle's high beams, otherwise the WoF inspector will turn you away and police cruisers may take a sudden interest.
The rule is so oncoming drivers aren't blinded by a zillion-candlepower light show.
However, going from high beams plus driving lights to dimmed lights only in the time it takes to flick a switch can be disorienting; always be prepared to adjust to this sudden change.
A cheaper but often effective alternative to additional lights is to fit upgraded bulbs into the headlights. Talk to an auto electrician about the possibilities. Improved bulbs made a huge difference to one of Driven's editorial cars.
Foglights are also popular add-ons, although they're often standard on higher-grade versions of many vehicles. Their job is to cut through the murk, not provide long-distance illumination. But before buying a set, think about how often you actually encounter fog.
Add-on lights are usually round or rectangular, or sometimes oval. The shape generally makes little difference to the characteristics of the beam (although bear in mind top-model lamps are both large and round and there must be a reason); alternative shapes are mainly for reasons of styling and fitment.
Very small projector-beam lamps using compound elliptical reflectors have become popular. Their advantage is their small size that's great for placement and not restricting airflow to the radiator.
There's a huge price range in aftermarket lights. When buying cheap, you may be getting only what you pay for. Apart from such important considerations as the quality of beam spread, cheapies may not be particularly well constructed. Good build quality is important to avoid the possibility of corrosion and condensation.
Even modestly priced lighting from well-known companies should be of adequate quality. What's not so certain is the quality of cheap "generic" lamps that might carry a brand name you've never heard of. It's worth asking around for others' experiences.
Plastic doesn't necessarily mean bad, by the way. Some high-quality lights are of rugged polycarbonate or polycarbonate and metal; but you don't have to be a genius to tell these from the rubbish. For example, look at the finish and the quality of the mounting attachment. Can the mounting bolt fall off into the body cavity?
There's no point buying a good auxiliary lamp and hooking it up with inadequate wiring. Because good wiring has such an effect on a light's performance, many top brands include a full loom and a decent switch, all designed to let the volts get to the filament.
Even then, some cautious light-fitters will throw the factory stuff away and use even heavier wiring and switchgear. The relay, too, needs to be a quality unit.
