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d to arise. First, the variable costs of maintaining different types of roads differ significantly. According to Heggie and Vickers (1998), this ranges from;

0.026 to 0.177 cents per vehicle/km on main road network

1.499cents per vehicle/km on high volume local access roads

1.035 to 1.321 per vehicle/km on rural road network

The total costs of maintaining different types of roads also vary from:

a low of 0.224 cents per vehicle/km on the main network to

a high of 7.637 cents per vehicle/km on the rural road network.

If road charges are strictly based on costs, then this would involve wide differentials between different types of roads and different central and local government road agencies. A practical set of user charges should therefore involve a great deal of averaging.

Second, the variable costs of maintaining the road network also differ significantly with vehicle type. Cars impose relatively small costs on the road network while articulated trucks impose costs almost 12 times larger (Heggie and Vickers 1998). In principle, an articulated truck should therefore pay 12 times more than a car. If the main charging instrument is fuel levy, the articulated truck will only pay three and a half times more than a car since, on the average, it takes in about three and a half times as much fuel as a diesel car. This problem can be avoided by switching to weight - distance fees which can be more accurately calibrated to reflect underlying road- use costs.

The final problem relates to how license fees and fuel levy are set to ensure the variable element of road tariff paid by each class of vehicle (the fuel levy) covers the variable costs that their vehicles impose on the road network and that the road tariff, taxes and other charges used to support local access roads collectively cover all road costs.

The fuel levy by itself as illustrated above, tends to generally undercharge articulated trucks while overcharging other vehicles, particularly buses. Prior to its abolishment in Kenya, the road license fee was used more as an access fee, set to cover only fixed costs. In view of the illustrated shortcomings of fuel levy as an instrument, it is imperative that license fee be used to compensate for it. The combined license fee and fuel levy should therefore be set to ensure that each vehicle class covers the variable costs it imposes on the road network.

3.0 ROAD NETWORK FINANCING OPTIONS 道路网络融资方案

Based on the above outlined model on appropriate charging instruments and efficiency pricing, we propose the following road maintenance, investment and rehabilitation financing options for Kenya.

3.1 Financing Maintenance
Our funding framework suggests that the costs of operating and maintaining the inter-urban road network should be financed through the road tariff. For roads in the urban and rural areas at least the variable costs of operating and maintaining the network should be financed through the road tariff. The balance of the required expenditures in urban and rural roads should then be financed from local revenues, such as parking charges, cess, local property, taxes etc.

An important feature of this framework is that it focuses attention on the affordability of a fully fund