There is an apparent decline in the road network condition for the unpaved TMD from 2004 to 2009. The roads in fair condition have slid into the poor condition. The decline is clearly noticeable from 2007. Possible insights into this scenario could be stated as follows:
3 Future Network Condition Criteria
Table 3-1 shows the trend in the overall condition on Zambia’s paved Trunk, Main and District Roads since 2006. An assessment has revealed that the present ROADSIP II roughness criteria was too high compared with the maintenance options limits, thereby increasing the expenditure to maintain the road network unnecessarily. This lead to the introduction of a revised set of criteria for the condition of the paved road network where it was observed that a good road will not require more than routine maintenance and this is fulfilled for a roughness less than 4.5 and all traffic ranges. A revision in the ROADSIP II criteria as observed in Table 3-1, has seen the bulk of the paved network on TMDs falling in a good condition rather than fair condition with the previous criteria which has a tremendous bearing on the maintenance budget of the network.
Table 1.1: Condition based on Total Paved Road Network
|
Condition |
% of Network 2006 |
% of Network 2007 |
% of Network 2008 |
% of Network 2009 (RoadSIP II) |
% of Network 2009 (Proposed RoadSIP II) |
|
Good |
29 |
19 |
33 |
18 |
75 |
|
Fair |
64 |
71 |
61 |
76 |
24 |
|
Poor |
7 |
10 |
6 |
6 |
1 |
For future road condition data collection, the network condition criteria shall conform to what is proposed in table 3-2. This method offers a more robust performance assessment of the network both paved and unpaved than what was used earlier under RoadSIP II. This is the criteria that is been used in the Zambia Highway Management System.
Table 3.2: Proposed new ROADSIP II Criteria
|
Condition |
Criteria For Paved Roads (m/km) |
Criteria For Unpaved Roads (m/km) |
|
Good Fair Poor |
IRI < 4.5 4.5 < IRI < 9 IRI > 9 |
IRI < 6 6 < IRI < 12 IRI > 12 |