#2745  by WoodyZ
 Tue Jan 20, 2009 7:21 pm
There is another weight that you do need to know.
When I do finally get my show on the road, I will have six (how did I get six, I meant four, silly old fool) axles to worry about, but apart from that, there is one bridge that we normally cross to get to a favourite spot that also has a maximum gross weight restriction of 4500kg and there are others around the country as well. My GCW will be in the order of 6500kg to 7000kg, so although I won't have much issue with most axle weight restriction bridges, Gross weight ones will be an issue in some places. :oops:
Last edited by WoodyZ on Tue Jan 20, 2009 8:12 pm, edited 1 time in total.
 #2748  by Mark
 Tue Jan 20, 2009 7:55 pm
OK Neil - thanks for pointing that out. So the previous summary
Now, when you are on the road you know two critical pieces of information:
a. Your maximum axle weight
b. Your maximum % of Class I loading

Now when you come to a weight restricted bridge, it's easy:
- If your maximum axle weight is greater than any weight specified in kg's - Don't cross
- If your % of Class I is greater than the percent specified - Don't cross
can be modified to this (just so it's all in one place):

Now, when you are on the road you know three critical pieces of information:
a. Your maximum axle weight
b. Your gross weight ie axle 1 plus axle 2 (for the simple 2 axle situation)
c. Your maximum % of Class I loading

Now when you come to a weight restricted bridge, it's easy:
- If your maximum axle weight is greater than any weight specified in kg's - Don't cross
- If your gross weight is greater than the specified maximum gross weight - Don't cross
- If your % of Class I is greater than the percent specified - Don't cross

Does that now cover what is needed?
 #101599  by razor
 Tue Oct 20, 2015 8:24 pm
when it comes to clyde bridge I go to alex being 8100 on rear twin tired axial
axial weight on the bridge is 6000kg
 #158391  by Travelbuddy
 Tue Jan 28, 2020 2:00 pm
Hi There
I am new to all this and I've found this discussion from some years ago re: bridge weight limits (copy of NZTA? information pasted below for your reference). To be clear that I have this right, does that mean if my truck weighs 6000kgs then I could not cross a bridge saying 30% of class 1? And if my truck weighs 5800kgs, then I can cross that bridge? I certainly don't want to end up at the bottom of a river!
Thanks so much for your help
Jenny
-----------
Thank you for your further email dated 31 December 2008.
The weight definition of a Class 1 licence is:

A vehicle that has a gross laden weight (GLW) or gross combined weight (GCW) of 4500kgs or less.
Therefore; the weight limit for certain bridges in the South Island would be as follows:

Vehicle weight which is 30% of class 1 - would be 1350kgs
Vehicle weight which is 60% of class 1 - would be 2700kgs
Vehicle weight which is 90% of class 1 - would be 4050kgs
Vehicles over 30% of class 1 - have a weight limit of 5850kgs
Vehicles over 60% of class 1 - have a weight limit of 7200kgs
Vehicles over 90% of class 1 - have a weight limit of 8550kgs
If you are driving a vehicle that weighs more than the recommended weight for any bridge in the South Island, you would have to find an alternate route to your destination.
 #158399  by don.robinson
 Tue Jan 28, 2020 7:33 pm
Hello Travelbuddy / Jenny

Class One weight limits depend on the axle configuration and tyre type. Single tyres, twin tyres,etc. not to be confused with the Class One Drivers license. Bridge posted weight limits are not related to Drivers license categories and I find the table listed in your email rather awkward to interpret and will easily lead you astray. I suggest don’t use it. Some of the other information from earlier dates posted under this Bridge Limit heading is also difficult to understand easily.

I suggest:

Download the NZTA information with the heading:
“Vehicle Dimensions and Mass”
A Google search should bring it up, probably as the first item.

With a bit of careful reading it should make it all clear. If you are having trouble I suggest you use a highlighter to highlight the bits that are relevant to you and don’t worry that it is only a small part of the whole document.

Simplified though, the Class One weight limits as applied to Bridge Weight Limits can be thought of as being in two parts.

Part one is axle weight:
Single normal tyre each end of a single axle. 6000 kg axle weight
Twin tyre each end of a single axle. 8200 kg axle weight
Other axle configurations are possible but these two cover a majority of MH’s.

Part two is the total vehicle weight:
Calculated by summing up the individual axle weights.

Bridge axle limit weights are usually posted as a % of the Class one axle weights.
OR
There may be a total weight limit as a % of Class One, or maybe a total weight limit in kg.

I hope this helps and does not confuse you. In your particular case, you can see that there is not enough info in your post for me to do an example calculation as I don’t know the axle / tyre types. The reason for the two parts to many Bridge Weight Limits is that the two main failure modes in an overloaded bridge are the bridge main beams and as a quite seperate issue the bridge decking and other parts that spread the load.

Don Robinson
 #158408  by Travelbuddy
 Wed Jan 29, 2020 11:13 am
Thanks Don. It's fair to say I am completely confused!
I am in the beginning stages of building a motorhome now, which will be on a 6 tonne truck base. So I'll speak to the builder about it all and when we have the exact truck, then I will know exact weights.
Thanks so much for responding. I look forward to touching base again when I have more info about my particular vehicle!
J
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