Who said that visibility was more than 100m. Frequently, waterlogged road surfaces will produce considerable spray such vehicles less than 100m ahead are barely (if at all) definable, - as @PeterMugridge posts, cases of inadequate visibility of vehicles ahead due to heavy spray does occur. My eyesight is not inadequate for driving in any conditions that I deem viable, - however, visibility of other vehicles should be better than just discernable in a cloud of airborne spray to be able to detect it's movement and any unexpected changes in position.
To be more specific, in my experioence much of the poor conditions of spray occurs on multi-lane roads (e.g. dual carriageways and motorways) where vehicles in adjacent lanes can make conditions worse in seconds. Some people have some extreme aversion to high intensity rear lights and for their part claim that any use other than in fog so thick that they can't see is dangerous to all. Fortunately not everybody agrees with their assertion. Driving is not a competition to see who can see the furthest in poor conditions.
The 'traditional' way of measuring human weight is Kg, and has been since the 1960s when the UK formally adopted metric weight. The dwindling numbers of the population still stuck in imperial measures is an ancient tradition. Lucki9ly, the NHS and all other heath concerns use the current measure.