15, 25, 35, 45, 55, 65, 75, 85, 95 - why ?

[Slyer]

What I want to know is how they decide what corners to put them on.
You'll often see fairly sharp corners that are missing them.

[Supertwin Don]

nah, don't agree here.

signs are designed to show the safest speed around the corner for cars.

Trucks depend if they are loaded. If under heavy load I know for a fact that they have to take corners at 20 km'h less than thesafst designated speed. This is due to the physics and geometry of the truck under load.

The ADVISORY signs don't have anything at all to do with "safest speeds" - safe speeds depend on conditions at the time - speed signs show maximum LEGALLY allowable OR maximum COMFORTABLE in perfect conditions - FOR CARS ONLY.
We used to say that anything with a 30kph or better sign could be got round at the numbers shown in miles per hour!
but the ones less than 30kph were definitely tight!

If a sharp corner doesn't have a sign, it usually means that it is OBVIOUSLY a sharp corner - and, after all is said and done, it's the rider who sets the speed!!

[Slyer]

Can the courts use these signs to say that you were speeding?
Like if you were doing 80kph around a 35 corner in a 100k zone, could they say that you were pushing it too much?

[Ixion]

Not directly. Cop can see you go round a 35 posted corner at 100, and he can't do anything (assuming it's a 100 zone). But -- if you crash trying to get round that 35 posted corner at 100, the fact that you were way over the recommended speed could be used to substantiate a careless driving charge (or worse, i guess) .

[jim.cox]

What I want to know is how they decide what corners to put them on.
You'll often see fairly sharp corners that are missing them.

That depends on the Road Controlling Authority - either the local council or NZ Transport Authority for state highways.

Someone there has a budget for signage, someone mentions the need and then maybe it gets signed.

Or maybe not, depending on how slack they are and how tight the budget.

Its probably worth mentioning it to the roading engineers if you do get a big surprise.