There are a number of debates raging including; how many discrete condition rating categories a system should use and whether a low number or a high number is good/bad, etc.
Optimum Number of Condition Categories
5, 10 & 11 Category Condition Rating Systems are the most common, but other systems have been used, and each system has its pros & cons.
5 Category Condition Rating Systems
Proponents of 5 Category Condition Rating Systems argue that they are simple to apply in the field and that it too difficult to identify the difference between assets in adjoining condition categories in a ten category system, e.g. between a footpath in condition 8 and a footpath in condition 7.
The International Infrastructure Management Manual gives the following example of a 5 category system. Please note that the IIMM was jointly produced and is promoted by the IPWEA as a potential standard for Asset Management. A significant number of Councils (particularly in NSW) are using this manual as a defacto standard for developing their asset management plan and activities.
Obviously, assets can have a remaining life of anywhere between 0% & 100%, so equating a condition score with a range of remaining lives better reflects the actual situation, say.
One advantage of the above approach is that all asset lives need not be reset to one of five distinct values following a condition inspection program.
For example, if an asset has a RUL of 65% and a condition score of 2, its RUL can remain the same.
If on the other hand is has an RUL of 65% and a condition score of 1, its RUL can be adjusted up by 20% to 85%.
This methodology has the advantages of the simplicity of a 5 point system without the problems caused by it, i.e. clumping of RUL's.
10 Category Condition Rating Systems
The proponents of 10 Category Condition Rating Systems argue that a 5 point scale is too coarse. That, if 1 is brand new and 5 is unserviceable there are only three other scores to choose from.
Please note that this 10 Category Condition Rating is compatible with the IIMM standard (if more granularity is required)
11 Category Condition Rating Systems
LG Asset Program promotes an eleven category condition rating system.
0 = A new asset or an asset recently rehabilitated back to new condition.
1 = A near new asset with no visible signs of deterioration often moved to condition 1 based upon the time since construction rather than observed condition decline.
2 = An asset in excellent overall condition. There would be only very slight condition decline but it would be obvious that the asset was no longer in new condition.
3 = An asset in very good overall condition but with some early stages of deterioration evident, but the deterioration still minor in nature and causing no serviceability problems.
4 = An asset in good overall condition but with some obvious deterioration evident, serviceability would be impaired very slightly.
5 = An asset in fair overall condition deterioration in condition would be obvious and there would be some serviceability loss.
6 = An asset in Fair to poor overall condition. The condition deterioration would be quite obvious. Asset serviceability would now be affected and maintenance cost would be rising.
7 = An asset in poor overall condition deterioration would be quite severe and would be starting to limit the serviceability of the asset. Maintenance cost would be high
8 = An asset in very poor overall condition with serviceability now being heavily impacted upon by the poor condition. Maintenance cost would be very high and the asset would at a point where it needed to be rehabilitated.
9 = An asset in extremely poor condition with severe serviceability problems and needing rehabilitation immediately. Could also be a risk to remain in service
10 = An asset that has failed is no longer serviceable and should not remain in service. There would be an extreme risk in leaving the asset in service
Cairns Regional Council uses an 11 point rating system, but in reverse order:
10 = Brand new
9 = Excellent Condition (90% of life remaining)
7 = Very Good Condition (70% of life remaining)
5 = Good Condition (50% of life remaining)
3 = Fair Condition (30% of life remaining)
1 = Poor Condition (10% of life remaining)
0 = Unserviceable (No useful life remaining)
This has the advantage of a direct relationship to remaining useful life instead of a reverse one.
However this is at odds with the IIMM and consequently would restrict access to data and information being held/shared with other councils who follow the IIMM structure for condition rating. It also appears that this form of condition rating with 10 = Brand New would be at odds with new legislation to be introduced in NSW in early 2009 (where 1 = Excellent or brand new)
- Asset Condition Evaluation Guide
- Condition Assessment Techniques
- Footpath Condition Inspection Sheet