Tarmac is the short term for Tarmacadam or tar penetration macadam. It is also known as asphalt concrete. This type or road surfacing was introduced originally by Scottish engineer John Loudon McAdam, thus the term, macadamisation.
The aim of McAdam was to replace the soil that gets muddy when wet. However, this road improvement became a problem because of the dust it emits from the layer or stones. It was not until Edgar Purnell Hooley discovered the use of tar. While working as a county surveyor, Hooley noticed a barrel of spilled tar on the road. Whoever spilled the tar tried to cover the tar with gravel. He noticed that when it dried, it was ideal for the road and dust-free. This was where his idea of tarmac came about.