View Full Version : 15, 25, 35, 45, 55, 65, 75, 85, 95 - why ?
I was doing some of my favourite roads today and round the twisties a question got into my head.
Why are all signposted corners as one of the following: 15, 25, 35, 45, 55, 65, 75, 85, or 95 km/h ?
Why isnt there any corners that we are supposed to take with 30 km/h or with 50 km/h exactly. Why the 5 in all those recommended speeds ? how about corners with 43 km/h ?
my riding knowlage is only in the north island so I dont know about the south, but I have NEVER seen a sign for recommended corner speed, with a round number on it.
Is there a reason behind it? If yes, is it physical ? Is it psychologycal ? Is it like one of those $199.99 psychological bargains in the shops ?
can someone enlighten me please.
cherio.
Yes. There is a reason.
Compulsory speed limits (ie get a ticket for exceeding them ) are (normally) in EVEN numbers. 30, 50, 60,70,80, 100
Recommended speed limits (no ticket if you ignore it) are in odd (multiples of 5 ) numbers . As you observe.
This is intended to facilitate people not getting confused. Based on my observation that the majority of the population is permanently confused, I think it optimistic.
None the less, that is the reason.
Timber020
2nd May 2009, 21:07
I was doing some of my favourite roads today and round the twisties a question got into my head.
Why are all signposted corners as one of the following: 15, 25, 35, 45, 55, 65, 75, 85, or 95 km/h ?
Why isnt there any corners that we are supposed to take with 30 km/h or with 50 km/h exactly. Why the 5 in all those recommended speeds ? how about corners with 43 km/h ?
my riding knowlage is only in the north island so I dont know about the south, but I have NEVER seen a sign for recommended corner speed, with a round number on it.
Is there a reason behind it? If yes, is it physical ? Is it psychologycal ? Is it like one of those $199.99 psychological bargains in the shops ?
can someone enlighten me please.
cherio.
All speed limit signs end with 0's I guess it might be to avoid confusion?
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.
James Deuce
2nd May 2009, 21:16
I blame Swedish rounding.
I can't say I've ever seen a 95.
I have. I wondered why they bothered.
Yes. There is a reason.
Compulsory speed limits (ie get a ticket for exceeding them ) are (normally) in EVEN numbers. 30, 50, 60,70,80, 100
Recommended speed limits (no ticket if you ignore it) are in odd (multiples of 5 ) numbers . As you observe.
This is intended to facilitate people not getting confused. Based on my observation that the majority of the population is permanently confused, I think it optimistic.
None the less, that is the reason.
Quality answer as usual. thank you.
edit: oh and there is a 95km/h on the coro :yes: (saw it today)
I blame Swedish rounding.
indeed, it's all his fault
Headbanger
2nd May 2009, 21:25
my riding knowlage is only in the north island so I dont know about the south, but I have NEVER seen a sign for recommended corner speed, with a round number on it.
Drove the length of the South Island a couple weeks back, It seems the Put 20 signs on every damn thing mania hasn't yet hit the place. Barely saw any signs at all,In fact the lack of them was raised numerous times. Had to get out of the mindset that every corner,every slight blip in the road or patch of gravel would be signposted.
Of course it may also have something to do with the complete lack of people apart from tourists and the odd cocky, at night there was a lot of trucks.
MaxCannon
2nd May 2009, 21:26
Lots of 95kph signs on the way to Taupo via Matamata.
Seems pointless, if you can't get round the corner at 100 going 5kph slower isn't going to help. You should leave the driving to someone else.
jaymzw
2nd May 2009, 21:26
Could also be the government constantly banging the slow down message in to every New Zealanders head. We drive at 50 70 or 100 usually, these speed recommended signs are always lower than this.
Funny story, whilst learning to drive on my 15th Birthday i learnt two lessons from my old man.
1-always wear your seatbelt
2-all those signs are half the speed im allowed to go around the corner at
I have. I wondered why they bothered.
They must use them for corners that look sharp, so they put them there to let you know you don't need to slow.
MadDuck
2nd May 2009, 21:28
Lots of 95kph signs on the way to Taupo via Matamata.
Seems pointless, if you can't get round the corner at 100 going 5kph slower isn't going to help. You should leave the driving to someone else.
Yeah there is one or two....never really understood it myself. Then theres the 45Kms ones that just dont make sense as they are easily taken a "bit" faster.
Over on the Coast theres one that says 15kmh:zzzz:i thought and tried it my way:bash:
vindy500
2nd May 2009, 21:49
in a truck that 85 k sign really means it! not 100 as normal.... that was scary
rainman
2nd May 2009, 22:41
1-always wear your seatbelt
2-all those signs are half the speed im allowed to go around the corner at
1-always good advice :)
2-alternatively (on a bike), read them as mph, not km/h. Except for the corners on those wobbly bits heading towards Whangamomona from the Stratford end...
Freeatlast
2nd May 2009, 23:00
Over on the Coast theres one that says 15kmh:zzzz:i thought and tried it my way:bash:
Going west from Springs... (towards Reefton) before the Rahu saddle... there is another. Ignore at your peril.
Freeatlast
2nd May 2009, 23:30
Funny story, whilst learning to drive on my 15th Birthday i learnt two lessons from my old man.
1-always wear your seatbelt
2-all those signs are half the speed im allowed to go around the corner at
In good conditions, with a good line through the corner, in good conditions, number 2 works well. To most, most times. The presence of other road users, the possibility of fuel spills on the outer of the corner apex, the possibility that you have taken the wrong line into the corner, the possibility of pot-holes in that corner, all conspire to make your life painful at times.
We all do it... but we all get it wrong, now and then. If you have'nt, you will.
sil3nt
2nd May 2009, 23:35
The only 95kph corner i can remember. Its nicely cambered although a little bumpy!
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monkeymcbean
2nd May 2009, 23:45
Its most likely the population thing, but working in the signwriting industry, Transit are pretty tough down here on people putting any sign up willy nilly so to speak, long may it last
Freeatlast
3rd May 2009, 00:11
Its most likely the population thing, but working in the signwriting industry, Transit are pretty tough down here on people putting any sign up willy nilly so to speak, long may it last
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.
Forest
3rd May 2009, 04:29
I have. I wondered why they bothered.
I always assumed they were put in for the benefit of trucks.
mctshirt
3rd May 2009, 07:24
My rule of thumb is add 10kph to their suggestion. Gotta be careful because occasionally they're not kidding :eek5:
I find it's a bit like Road Works signs at night - slow down a bit , check out if there really is anything being dug up and proceed as if nothing happened but occasionally they leave the signs out for a reason and that 4 inch drop on to thick gravel at speed is an arse puckering moment :sweatdrop
paturoa
3rd May 2009, 07:48
There used to be a bunch on scenic drive in orkers till about 2 years ago when they were all changed to ending in 5.
Over on the Coast theres one that says 15kmh:zzzz:i thought and tried it my way:bash:
There`s also a 15kmh corner on the Coromandle( , check out Blackbirds profile pic.
Logistics. If corners were rated from 15kph to 95kph in 1kph increments you'd need to have a range of 81 different speed signs on inventrory. Having them in increments of 5kph means you only need 17 different signs in inventory (unless they actually make them up to order?)
I like to think of the 15,25,35 etc signs on corners, not as a speed indication, but as a percentage of how much throttle to be using whilst riding around it..
yes I only had a 250, but it worked :D
On a side note
Theres a 80kph bit of road up here, out to snells beach, they have been doing road works on it for a while...posted 30kph area, when you get out of the 30k area, the speed limit is now 100kph....but its still a posted 80kph road.
nallac
3rd May 2009, 10:02
On a side note
Theres a 80kph bit of road up here, out to snells beach, they have been doing road works on it for a while...posted 30kph area, when you get out of the 30k area, the speed limit is now 100kph....but its still a posted 80kph road.
the good thing with those road works (besides being finished now)is that they didn't put the double yellow lines back..
pritch
3rd May 2009, 10:10
2-all those signs are half the speed im allowed to go around the corner at
Trying to take some of the 15 and 25kph corners at double the posted speed could be quite ummm thrilling(?).
Shame about the bike though... :whistle:
I like Shaun Harris' advice, "Take the slow corners slow..."
JacksColdSweat
3rd May 2009, 10:18
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
3rd May 2009, 10:22
Yeah here it is - a Ball Bank Tube....
http://www.monash.edu.au/cemo/roadsafety/abstracts_and_papers/127/F-N-Tate.pdf
And the numpties from Monash in Victoria have a comment about it...
xwhatsit
3rd May 2009, 11:24
My rule of thumb is add 10kph to their suggestion. Gotta be careful because occasionally they're not kidding :eek5:
Yep -- on the Coro Loop there's a couple of 15kph corners, that surprisingly really are about 15kph!
yungatart
3rd May 2009, 11:35
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
3rd May 2009, 11:53
there are some up north ound twin bridges that are 40 kph,first time i had see that too
i had always wondered this as well untill i started designing roads (dont hate me for that:dodge:) 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 :woohoo:
McDuck
3rd May 2009, 12:22
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
6th May 2009, 22:50
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
6th May 2009, 22:59
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
6th May 2009, 23:04
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
7th May 2009, 00:47
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
7th May 2009, 19:58
Over on the Coast theres one that says 15kmh:zzzz:i thought and tried it my way:bash:
yea there's a 15k'er on the way out to the whangmomana pub as well. And they mean it too...
The Pastor
7th May 2009, 20:12
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
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.
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 .
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
8th May 2009, 00:24
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!:Oops:
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!!
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?
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
8th May 2009, 12:46
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.
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