1.1 Background
The Core Road Network (CRN) infrastructure in Zambia consists of a sparsely interconnected network of trunk (T), main (M), district (D), primary feeder (PF) and urban (U) roads administered by the Road Development Agency. The Core Road Network is the bare minimum road network that Zambia requires to be maintained continuously and on sustainable basis so as to unleash the potential in the country and its people to promote self-development as the only approach to poverty alleviation for economic growth. This network is calculated at 40,113 km broken down as shown in Table 1.
|
Road Type |
Core Road Network (km) December 2002 |
|
Trunk (T) Main (M) District (D) Urban Primary Feeder (PF) |
3,088 3,691 13,707 5,294 14,333 |
|
Total |
40,113 |
In order to identify the most technically suitable engineering interventions for the CRN roads in good, fair and poor condition, the condition characteristics of the network were established using the surface condition criteria shown in Table 2. The criteria on paved road uses IRI, whilst on unpaved roads, the remaining gravel thickness is used.
Though there was a gradual increase of the road network in good condition between 2004 and 2006, there appears to be set back between the years 2006 and 2007, where there have been marked changes of roads sliding from good to fair condition. There is a notable increase in the condition from 2007 to 2008 and then slump from 2008 to 2009. The roads
The general trend is that the network remained generally stable with roads in good condition remaining fairly stable from 2004 to 2009, while there was a steady increase in the percentage of the roads in fair condition. The state of roads in the poor condition has steadily reduced with a corresponding increase in roads in the fair condition state. It should be noted that the general trend points to some stability for roads in the good condition state however, a slump can be seen from 2008 to 2009. Specific reasons for this have been highlighted below.
Fig 1-1: Net work condition Paved TMDs
Possible insights into the slump from 2008 to 2009:
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.