#123370  by don.robinson
 Thu Jan 19, 2017 4:32 pm
You would be OK on a bridge posted as 40% of Class 1, but normally the reasoning starts from the truck point of view.

Your figures show:
The front is 38% (2300/6000)
The rear is 30%
The total (gross weight) is 34%
Of Class 1 for your particular vehicle.

While you can say I am OK on a bridge posted as 40% of Class 1 it is more normal to know the individual percentages, because not all posted bridge limits are as simple as the photo in the orig. post. They can be posted as a gross vehicle weight limit and in addition an axle limit (which may not in fact be the same percentage).

You would be a small amount on the safe side with your approach using the limits in the photo but they may not always be that simple. It does tend to get more complicated when the bridge is longer.
I don't recall seeing a lot of limits on main roads recently but secondary roads, not used as much, may be a different story.

I hope this has not muddied things too much. Even a much more complicated bridge limit is readily calculated piece by piece if you know the gross weight and the axle weights of your vehicle.

 #123412  by Dusty
 Fri Jan 20, 2017 5:37 pm
Don , can you please post a link or reference to the class 1 max weight .

I see plenty of 44000 kg trucks on the road , so they must be ok , eh?

confused .
 #123413  by petercw
 Fri Jan 20, 2017 6:16 pm
Thx Don..I understand what you are saying and have a record of my fully loaded weights and axles weights..
Yes it is a bit confusing but at least I am much better acquainted with things now.
 #123416  by don.robinson
 Fri Jan 20, 2017 6:58 pm
Dusty, look at the second posting on page 1 for the LTNZ reference.
It lays out the info you want.

No simple answer as it depends on what axles you have and at what spacing and wheel style.

 #123419  by Dusty
 Fri Jan 20, 2017 9:05 pm
Thanks Don , I have spent ages reading thru that and I understand how heavy my vehicle is and what its axle loads are .

But I cannot understand what class 1 is.

When the sign says x% of class one , I need a number so I can see that I am within the load limit. What is a class 1 road weight limit . surely that is what can be driven on by a max loaded truck. Like State hwy 1.

I see the class 1 signs occasionally on the road side , but the point of reference is lost on me without a base number ........

OR is class 1 an axle limit ?? I cannot find that either :(
 #123427  by don.robinson
 Sat Jan 21, 2017 1:34 pm
From memory, without researching it, the following is an outline of the situation as to What Class 1 is.

Historically there were 3 classes of road, Class 1, 2 and Class 3. The Class 2 and 3 were then wiped and I can't remember exactly when, but many years ago ( more than 35 years).

Roads are now all Class 1, but also there are combinations of roads (Routes) which are classified for higher than Class 1 loads on a one by one basis. It depends on an economic argument and probably will never apply for Motorhomes.

So, most heavy rigid vehicles are subject to Class 1 restrictions as laid out in the LTNZ fact sheet. This means any particular style of heavy vehicle has a Class 1 allowable load. It varies by axle type, axle spacing etc. which is why when a bridge restriction is posted, it is as a % of Class 1. That is, it is the individual vehicles Class 1 weights, not the absolute maximum allowed on some other style of axle, truck or combination.

From memory, the maximum Class 1 weight is 44 tonnes for an individual truck or combination. The maximum applies to a particular combination of axle types and spacing rules which is why commercial operators shout loudly when alterations are proposed which affect their Rigs which were often specially built to carry a specific max load.

None of this really needs to concern you as a Motorhome user. Also please remember this is an outline from my memory. If you have specific needs you will need to research the situation in detail and not rely on this information.

In summary, your vehicle has its axle layout, for which there is a max Class 1 loading. In the original post example the max Class 1 load is 6000 + 8200 kg = 14 200 kg because of the axle/tyre types. These figures also apply to my own MH as it's axles are the same layout.
A 44 000 kg truck combination has enough axles/ tyres etc that allow it to be at that 44 000 kg weight on a Class 1 road.
It is in effect an axle loading restriction and the combination of the axles which leads to an allowable gross weight. Many trucks ( MH on truck style chassis) don't get close to the allowable gross weight for the style of vehicle. Any truck, no matter what total weight, is restricted to 6 000 kg on a single tyre axle but also subject to spacing restrictions from other axles.

I hope this helps. If you are still not sure what it all means, I doubt I can do much better in a Forum post without writing a text book - which I don't want to do.

 #123432  by Dusty
 Sat Jan 21, 2017 7:03 pm
Thanks for the huge response Don .

So if I understand correctly , my bus has single tyres on the front axle and duals on the rear and the weight restriction is just for the axle loading for my bus , not for the total road load that might be imposed by any vehicle .

I gotta go re read that stuff again (and again) :) and try to figure out my axle max loads.

Thanks again Don.
 #123449  by Mick
 Sun Jan 22, 2017 9:19 am
still confused...
The sign says "GROSS 20% of Class 1", no axle weights etc. mentioned. So as of my interpretation "Class 1" should be equal to a defined absolute value => Dan mentioned it means (could mean) 44 tones.
As a result I would then assume the bridge is limited to 8.8 tones (20% x 44t). If the bridge is so long that a towed vehicle and the bus stand on the bridge in the same time then still 8.8t is the absolute limit in whatever constellation.
How's that?

Cobb Valley road / bridge at generator house: Gross 60% of Class 1

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