Road Pavement Useful Life

Methodology for Estimating Asset Life from Consecutive Condition Assessments

Table 1

The table below shows example (made up) PCI data for road segments re-inspected after 5 years.

Year 0 Condition Year 5 Condition Average Condition Annual Rate of Change
15 30 22.5 3
25 55 40 6
33 51 42 3.6
45 75 60 6
48 79 63.5 6.2
56 100 78 8.8
58 98 78 8
66 90 78 4.8
75 85 80 2
82 102 92 4
85 112 98.5 5.4
89 122 105.5 6.6
91 132 111.5 8.2
95 115 105 4
101 129 115 5.6
110 139 124.5 5.8
115 133 124 3.6
120 171 145.5 10.2
121 155 138 6.8
125 156 140.5 6.2
128 165 146.5 7.4
129 150 139.5 4.2
135 170 152.5 7
139 175 157 7.2
141 166 153.5 5
150 220 185 14
160 5 82.5 -31
175 6 90.5 -33.8

The last two points are meant to represent roads that have been reconstructed in between inspections are excluded from the analysis. The remaining points are graphed below.

PCI-Graph1.png

A quick bit of high school math

Rate of Change of Condition = A * PCI Score + B

You could do a least mean squares fit if you want to, but for this example I have just picked a line by eye.
(It would be nice if real data follows an obvious pattern, but I suspect real data will be equally scattered).

The red line runs through the points (0,2) & (157,7.2)

Which gives the equations:
2 = A * 0 + B - (1)
7.2 = A * 157 + B - (2)

Therefore B = 2 and A = (7.2-2)/157 = 0.033121019

Which gives the equation: Rate of Change of Condition = 0.033121019 * PCI Score + 2

It follows that : PCI (year n+1) = PCI (year n)*1.03312019 + 2

This yields the following graph

Example-Condition-Curve.png

And the above graph not only gives you a way of semi-scientifically determining a useful life for road pavements, it also lets you estimate the expected remaining useful life of any road segment you have a condition score for.

Depending on your scoring system and construction standards an assets initial condition may not be zero.

If for example a typical road has a PCI of 10 immediately after construction, and you have adopted a service level that roads should be reconstructed when the PCI is greater than 200, a typical road would have a useful life of 40 years.

Example-Condition-Curve-2.png

For a better result you would probably need to create graphs for a series of road categories and traffic volumes.

Attachments

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License