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

[JacksColdSweat]

But they determine that speed by driving around the corner in a car with a device that measure's the centripital force

That speed (rounded to the nearest 5) is the speed a car will go around that corner in the middle of the lane with minimal centripital force trying to take you off the road..

or summit like that...

bring on the flames...

[JacksColdSweat]

Yeah here it is - a Ball Bank Tube....

http://www.monash.edu.au/cemo/roadsa...7/F-N-Tate.pdf

And the numpties from Monash in Victoria have a comment about it...

[xwhatsit]

My rule of thumb is add 10kph to their suggestion. Gotta be careful because occasionally they're not kidding

Yep -- on the Coro Loop there's a couple of 15kph corners, that surprisingly really are about 15kph!

[yungatart]

Lots of 95 corners between Wanganui and New Plymouth.
My understanding is that the corner speeds are an advisory speed for cars and a truck upper speed limit. If a truck rolls on a corner with such a speed sign, chances are the truck exceeded that speed and will be charged.
I'm sure a truckie can elaborate....

[spookytooth]

there are some up north ound twin bridges that are 40 kph,first time i had see that too

[NOID]

i had always wondered this as well untill i started designing roads (dont hate me for that) it is all to do with the curve radius, camber etc etc (long draw out process) so in the end you design a corner for 80km but you have to post it as 75..... then wen you drive it you double the indicated speed just for fun

[McDuck]

I have. I wondered why they bothered.

I think it is pro-active. If it is a road that people normally do 130 down then they (may) need to know about it.



But i always read the road conditions rather than the sign.

[monkeymcbean]

Transit only get upset at other people putting up signs. I was in Queenstown today, The Kawerau gorge has plenty of "recommended" speed signs. The only ones that were obeying them were in rentals.

Well they need to, hope they where they on the correct side of the road? Not a bad road to ride, and you do luck out sometimes with not many sharing it with you, not that im selfish! Where you on your bike?

[monkeymcbean]

I think it is pro-active. If it is a road that people normally do 130 down then they (may) need to know about it.



But i always read the road conditions rather than the sign.

I guess everyone is different and what speed you choose to go in certain places is all based on your own personal judgement and experience, when i was touring unfamilar roads in the North Island comming up to bends i always read the recommended speed limits it just allowed me to prepare gears, bike position etc kept me thinking, you can get a little complacent riding for a few weeks and for all day.

[Howsie]

I would like to see most compulsory speed signs replaced with recommened signs over time.
I can't say I've ever seen a 95.

There is a 95kmph sign on SH1B.


They are a recommended speed sign as the most comfortable speed to take this corner at and most likely a maximum speed for trucks.

Obviously this will differ depending on what type of vehicle you are in/on. In the van i can add approx. 20kmph more than what the sign says without fighting my way uncomfortably around the corner. On the bike, usually double except for the 15/25kmph signs, they really mean it!

On a 55 corner i know i can do it at 100kmph on the bike, not in the van, not quite in your average car and possibly in a sports/modified/race car.

[Supertwin Don]

from the dark recess of my memory when working for the MOW / MWD some years ago, there are speed RESTRICTION signs (round, red border) and speed ADVISORY signs (yellow, black border I think)
Restrictions are legally enforceable speeds, Advisories are (as a man said) determined by a device measuring the amount of "sideways" force exerted when travelling around the corner - I remember it being a board with a curved spirit level which was positioned sideways in the middle of the car.
The idea being that a certain value was acceptable and any more was not.
The roads themselves are designed for a speed value in accordance with certain parameters for suspension / tyre adhesion/ road surface etc and were generally 60mph / 100kph - and then had a safety factor added in.
As you aren't supposed to do more than the posted limit there is no need to "design" anything for more than, say, 20% above that.
That said, advisories also take into account just where the bend is - if you fall off the 25k bends on the Kaikoura Coast, it's going to hurt!
Likewise near schools etc.

[lankyman]

Over on the Coast theres one that says 15kmhi thought and tried it my way

yea there's a 15k'er on the way out to the whangmomana pub as well. And they mean it too...

[The Pastor]

the signs are designed for trucks btw, cars n bikes can go alot faster SAFELY around the corner, like the 55 corners useally mean 60-70

[TOTO]

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.

[Ixion]

It's a good many years ago, but I remember discussion on this in motoring magazines when it was first introduced . NZ was one of the first in the world to do it.

From memory , the speed is set with a sort of sideways Tapley meter, and is based on a lateral force of only 0.2 G .