It depends on what type of signs. On road signs they may be speed limits or distances; on tankers, they may be indicative of hazardous substances.
Road signs are in miles. All other distances are metric.
Whichever department has authority over that specific road. E.g., for private roads, this may be determined by a Home Owners' Association or company which owns the property, county roads will be determined by the county, etc.
The humps do not affect the speed limit. The speed limit is determined by other rules and signs.
Road signs, Maps and Internet sights determine this by going from City Centre to City Centre.
The distance from London to Newton Abbot England is 303Km and the driving time is 3hrs and 3mins.+++NB: All road distances in the UK are measured legally only in Statute Miles, not km, so advice quoting English road distances should be in miles, to correspond to the road-signs giving distances and speed-limits, to published road-maps, and sat-nav calculations.
Road signs give information, warnings and instructions.
Guide signs
You can get road signs painted on Road Traffic Signs's website. This website allows customers to customize their own road signs and they will ship them for a charge.
A road sign is a sign that is on the road. For example you will get signs to say how far you are mean't to go.
Stellar parallax
The standard, commonly used road signs are public domain.