Highways are arteries along which, after construction, interaction leads to development of the social hubs conjoined.
Roads have been designed and built by civilisations for thousands of years. Road building took place in ancient Egypt and Abyssinia up to 4 thousand years ago.
The Romans took road construction to new standards with their stone paved highways built for military operations, and later, social expansion.
Parts of some of these roads can still be seen in sites in North Africa and Europe.
They were built with drainage channels to both sides, and the spoil making for a gradient from the road centre for water run-off.
On a bed of compacted sand or dry earth, a layer of crushed rock and broken tiles were put, on which was a layer of gravel in cement mortar holding up a course of sand, gravel and cement into which the flat stone surface slabs were laid.
Modern construction methods and materials vary depending on the expected rates of usage and environmental requirements.
Earthwork is a major part of the process of road building, excavation and material movements, allowing the way to lay the base layer of loose crushed stone and sand to a depth capable of absorbing traffic loads whilst keeping the underlying subgrade from movement.
Commonly a bound base course is laid over the loose layer. Lime, cement or bitumen are the commonest used in binding.
When lime or cement are used as a binder it is recognised as hydraulically bound. When bitumen is used it is described as either hot or cold asphalt course depending on the temperature of the bitumen when used.
Most commonly in the UK, the paving or surfacing of the road is with asphalt. Concrete is used for roads which have to withstand heavy loads.
Environmentalism, longevity and recycling are becoming important components of highway building, from bridges to intersections and the road itself. Maximising the use of recycled materials has had a beneficial effect on the quality of roads and highways, and a correspondingly beneficial effect on the environment.
Ever increasing traffic levels and consequent increase in vehicle load, have led to underline the importance of construction management techniques. Today’s priorities are managing maximum traffic in optimal space, whilst maintaining or improving highway safety.
Designing a highway must, these days, given the density of modern traffic, have not only vehicular safety in mind, but pedestrian, cyclist and environmental safety all in the building mix.