††The first important development in road building was John Loudan Macadam's invention of a durable road surface made from crushed rock. The addition of tar, a waste product of the coal gas industry from the 1830s onwards, improved roads still further. Roads using the new material slowly evolved, usually built by private companies who would then charge tolls to use them.
Many recent roads are made up of huge slabs of concrete joined by bitumen, and the laying of new roads is now highly mechanised.
