Introduction to pavement thickness design: some basic considerations

Since the invention of the wheel in Mesopotamia (partly, today's Iraq) in about 5000 bc, and the subsequent development of the axle that joined two wheels and enabled heavy loads to be carried more easily, the ‘holy grail’ for travellers has been to move easily, quickly and safely on ‘pavements’ that can carry the imposed traffic loads in all-weather conditions.

Archaeological excavations show that diverse forms of road evolved in early times. Initially, these were natural trackways that became trade routes along which settlements developed. It is now well established that stone-paved streets were constructed in the Middle East about 4000 bc, brick pavings in India about 3000 bc and, in Europe, corduroy-log paths near Glastonbury in England c. 3300 bc, and stone roads in Crete c. 2000 bc. Starting in 312 bc, the Roman dictators used conscript labour to build a great military road system of some 78 000 km, based on 29 major roads radiating out from Rome; the function of these roads was to aid the imperial administration of the Roman Empire and enable its legions to quell rebellions after regions had been conquered. Many of these roads were built on embankments 1–2 m high, to give troops commanding views and make them less vulnerable to surprise attacks: in hindsight, this had the engineering by-product of keeping the pavement dry – which is probably why so many sections of Roman roads are still extant.