The viscosity grading system is more rational than the penetration grading system. Some countries, mainly India, use this type of bitumen. Bitumen is graded based on absolute viscosity at 60 ºC or kinematic viscosity at 135 ºC which are the temperature of the road surface in summer and the temperature of asphalt mixing, respectively.

This type of bitumen is divided as follows:

• VG-10 has extensive application in cold-climate paving and surface dressing. It is also used to manufacture Bitumen Emulsion and Modified Bitumen products.
• VG-20 is specifically used for paving in cold climate and high-altitude regions.
• VG-30 is a product derived from the oxidation process of vacuum bottom in a distillation tower and is classified based on its viscosity grade. Its primary application lies in the construction of high-strength bitumen pavements capable of withstanding heavy traffic loads. VG-30 bitumen is also extensively utilized in road construction, waterproofing, building construction industries, and also in cutback bitumen production suitable in rainy and mild regions.
• VG-40 is employed in high-stress locations like intersections, adjacent to toll booths, and truck parking lots. Its elevated viscosity enables the production of stiffer Bitumen mixes, enhancing resistance to shoving and other problems related to higher temperature and heavy traffic loads.