At the beginning of the 20^th century, cars began to spread and could then drive at speeds over 60 km/h (40 mph) on a road network that mostly consisted of gravel or dirt roads. In urban areas, drivers and wanderers were experiencing breathing difficulties because of the huge amount of dust generated by car traffic. In addition, drivers’ vision was impaired and many accidents occurred due to unseen obstacles. Last but not least, houses neighbouring trafficked streets became covered in dust and their indoor air quality was heavily degraded. Thus, dust emissions from pavements became one of the most pressing public health topics of the day.

Dr. Ernest Guglielminetti, a Swiss physician, observed that spreading coal tar on gravel roads could get rid of the problem (Figure 1). He thus heavily promoted its use in Monaco, France and Switzerland which owned him the nickname of Dr. Goudron (= "Dr. Coal Tar" in French) [1]. He is recognized as the father of modern pavement technologies and pioneered the development of organic binders for road paving applications. In a 1904 article, he advocated the spreading of coal tar in order to reduce dust emissions from pavements. He listed what was needed to make it work properly: coal tar dotation, dry support, temperature above 20°C (68°F), even pavement… Interestingly, he noticed that “la couleur noire que prennent les routes n’est pas très esthétique et soulève bien des protestations” (“roads are now becoming black and this is generating a strong aesthetical concern”) [2].

Obviously, this drawback didn’t prevent the widespread use of black paving products and society could easily cope with this reality. Still, architects started to ask for other colour choices and in the 1960-70s, it became more and more common to see dark red asphalt mixtures. They were obtained by using red pigments in combination with low-asphaltenes binders, because it was recognized that asphaltenes were the bitumen components largely responsible for its black colour (see RoadMat Note 8 on bitumen structure). However, the colouring power of asphaltenes is so strong that no other pigment could compete and for long, only this typical brownish red asphalt was available. So, formulators started to work on bitumen substitutes in order to propose binders that would mimic bitumen in terms of properties but with a transparent or clear colour that could be changed at will by adding the right pigment. Several suppliers proposed such products in Europe, USA and Asia.