Trésaguet, Pierre-Marie-Jérôme (1716-1796)

French civil engineer who introduced improved methods of road building.

Trésaguet was born in Nevers and worked for the Corps des Ponts et Chaussées on civil engineering projects. He eventually rose to inspector general.

Trésaguet realized that lasting improvement to roads could be made only by providing a solid foundation, one that could withstand winter rains and frost, and the effects of traffic. He chose to dig out the roadbed to a depth of about 25 cm/10 in and lay first a course of uniform flat stones, laid on edge to permit drainage. Well hammered in, they provided a solid base on top of which he spread a layer of much smaller stones for a smoother surface. His roads were built 5.4 m/18 ft wide, with a crown that rose 15 cm/6 in above the outside edge.

His method was first used for a main road that ran from Paris to the Spanish border, via Toulouse. It proved so successful that many other countries copied the idea.