Principles of Rail Traffic Management

The proposals for the Ethiopian national network envisage a self‐sufficient system, particularly in view of the cheap hydropower generation which will be used to power the majority of the operational railway, when this is completed.

However, the key to an efficient railway is the way in which assets are used. Use too near capacity leads to problems of unreliability, as there is no “slack” or spare capacity in the system to cope with any problem. Too little use leads to financial problems, as costs are not spread widely enough. The UIC’s suggestion of only planning to use 75% of line capacity is a helpful indication of what is appropriate.

Rail line capacities are maximised when there is a limited range of train speeds. Fortunately, suburban or stopping passenger services often have a similar end‐to‐end speed as freight services, as can be shown by parallel lines on train graphs.

Higher speeds can help the asset utilisation of rolling stock, but (of course) at the increased expense of infrastructure maintenance and additional operational and maintenance costs. Truly high speeds (150kph+) are not recommended in the Ethiopian context at this stage, as it is thought unlikely that traffics would sustain the higher prices needed to support the higher cost base. However, operating speeds between stations of (say) 120kph are eminently more marketable than those of (say) 60kph, and have the added advantage that fewer trainsets are needed to support the same train service. Also, future speed enhancements of both passenger and freight trains must be assessed and provided for during the initial infrastructure design process.

Sufficient work has now been undertaken to make different line speed assumptions over different line sections. For instance, 120kph average speed may be achievable for passenger services over the favourable terrain between Mojo and Shashemene, but 70kph seems more likely in the Arba Minch area.

One of the advantages of NRNE being a relatively late development in the railway field is that best practice can be adopted from elsewhere. In timetabling terms, development and utilisation of regular‐ interval services is obligatory. Whilst some research has been undertaken on their positive impact on demand. It is recommended that the services proposed for NRNE follow these principles wherever possible.

Freight train planning is generally more difficult than that for passenger services, which are more regular. Moreover, the costs associated with ‘tripping’ a few freight wagons between yards and sidings can constitute 80% of the costs of wagonload freight, which suggests that trainload working is to be encouraged. However, wagonload freight may be a political requirement, in which case its efficiency would be improved if timetabled daily services were organised, with strict attention to the loading and unloading of wagons in yards, so as to maximise wagon utilisation. This is likely to be important in an environment where many of the commodities which may be carried cannot use the same wagons e.g. cement, metal sheet, stone/aggregates and cereals.

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