Framework Conditions

Those involved in the planning and construction of minor rural roads often find that the financial means of the main contractor (rural commune, cooperative, individual) are limited and the project will have low priority among competing government activities. Moreover, these roads have to be planned for slow-moving, infrequent traffic, and, at the

Table 3.7. Definitions of some important technical terms


Design load Definition standard single-axle load or equivalent standard-axle load: 8.2 t or about

80 kN (US: 18 kip [1 kip = 4.4 kN]) HMT Heissmischtragschicht: Hot-mix asphalt (mixed in plant), used as bearing bed and pavement

GIS Geographic information system: a system for capturing, storing, checking, integrating, analyzing, and displaying data about the Earth that is spatially referenced. It is normally taken to include a spatially referenced database on appropriate applications software. LIS Land information system: a system for acquiring, processing, storing, and distributing information about land. CBR California Bearing Ratio

CBR% P • 100 P : resistance of the material in place

Ps : resistance of standard material ME Disk standard procedure

ME Ap ■ D [N/mm2] A P : change of change (pressure)

A S : corresponding change of settlement or [kg/cm2] D : Diameter of disk same time, designed to bear heavy loads. They should also be easy to drive on, should conform to appropriate standards in terms of safety and consolidation, and should offer sufficient comfort.

Although in many countries a complete set of standards for high-performance roads is readily available, these standards simply are not applicable to minor rural roads for a variety of technical and economic reasons. Generally speaking, there are considerably fewer regulations intended for minor rural roads than for the high-performance type. This allows greater freedom to those concerned in the modelling of such works (variants and selection criteria). Despite this fact, more assessments and decisions are required. Two main criteria are worth mentioning: utility and cost-effectiveness.

Conspicuous examples are found in the work of the pioneering Swiss bridge builder Robert Maillart. His celebrated bridges often are found on country roads and are fine examples of the conservative use of materials, which at the time was an important consideration in view of the higher relative costs of both materials and transport, as well as for the superlative and even daring way in which they are laid out [25].

For the following remarks we make reference to Hirt [24] and Kuonen [23].

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