QUOTE (dreamer21 @ Wed, 27 Aug 2014 - 11:08)
as the 40 sign was on the bend on the uxbridge road dual carriage way it took me 10 sec to make it out thats when i started slowing down.
Without being in any way sarcastic or condescending, if you really did have that much difficulty working out the sign (as opposed to exaggerating here for effect) then a trip to the opticians might be in order. Eyesight deteriorates slowly and you often don't really notice it changing and the brain is very good at lying to you about what you think you can see. Eyesight changes throughout your life, your body only matures at about 25 years old, and then people start losing their ability to focus in their 40s - some even earlier, and there are numerous other factors that can affect your eyesight. You may find that if you have vision issues, then night time driving is especially difficult.
The reduce speed now signs are advisory only, often to denote other hazards in the road, not just speed limits. It may well be that the RSN sign on the other carriageway is a reflection of the carriageway camber or bend being worse in the other direction.