We want good roads everywhere to facilitate the affordable transport of people and goods, but the Romans were perhaps the only civilisation who succeeded in ‘having their cake and eating it’. Their roads were robust and extensive but horribly expensive. Since then, to further entwine ourselves in culinary metaphors, we have had to ‘put water in our wine’ to achieve affordable access in many situations.Western civilization had first of all to rediscover how to design and build roads that were durable and economical. We are now faced with the problem of choosing the “good-enough road” (coined by the British child psychologist, D.W. Winicott to describe good parenting). In other words, the best for a given situation. If a road is under-designed, it will not fully exploit the benefits from improved service to users. Furthermore, it could be unstable and difficult to maintain under the combined assault of weather and traffic. If, on the other hand, it is over-designed, it will mop up funds that could be used for other roads or other purposes. Also, it will be costly to maintain to a high standard. Finally, destruction of the natural environment will be more severe, as the higher the the standard the more materials and energy will be used in the construction process.
The level of service a road should provide must be determined pragmatically. Although road engineers have a natural inclination towards fixed national standards, these are only useful when they can be justified by the vehicle operating savings they induce, a function of traffic volume and extent of improvement. Many models, such as HDM-4, exist for such analyses. Their applicability becomes more and more questionable when vehicles are few and savings are small relative to the cost of the road. Attention must shift to networks rather than links and formal model-building should be replaced by stakeholder consultation and strategic, security or social cohesion considerations. Integrated Rural Accessibility Planning (IRAP) can facilitate this process.
The choice of road quality and the technical characteristics of the road which will best provide it is a compromise between technical and cost considerations, fuelled by a natural desire for speed and comfort, and severely restrained by willingness and capacity to pay. Engineers should determine what technical specification is most appropriate, based on user needs, terrain, available materials and weather (see also low-cost road surfaces and structures). Environmental degradation must also be minimised by appropriate measures. Planners and designers should work with the stakeholders to determine the network they really want, once confronted with a full range of mobility options and their costs and armed with the information to make an informed choice amongst them.
In a limited resource environment, this decision process is vital when one considers that at the basic single traffic lane, engineered earth road with key watercourse crossings, labour based construction can be achieved to all-season passibility for costs in the order from US$10,000/km equivalent. This may be suitable for vehicular traffic of up to 50 vehicles per day if the insitu soils are suitable. Working up by initial cost considerations through gravel surfaced roads to more durable surfaces a two traffic lane concrete or asphalt concrete road could be costing of the order of US$500,000/km equivalent, or more. For further information on costing refer to What will it cost?
Road maintenance of course is an ongoing need and can be expected to cost between 2% and 15% per year of the initial construction cost.
So, the key sub-questions are ‘What is the road task?’ and ‘What initial and ongoing financial resources are available?’
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