In the past, the penetration index was defined based on the assumption that thermal sensitivity in the bitumen used in road construction was zero. Bitumen is a thermoplastic material that becomes pliable or moldable above a specific temperature and returns to a solid state upon cooling. Penetration-grade bitumen is mainly used in road surfacing. Bitumen with a lower penetration grade is used in regions with warm climates, while a higher penetration grade is used in colder weather. Maccoran Petroleum Company can supply different grades of road surfacing bitumen in compliance with national and international standards. Penetration rate bitumen is graded based on penetration and softening point tests. This table describes the physical properties of penetration-grade bitumen based on European standards. Penetration-grade bitumen is mainly used in road construction. During the last two decades of the 20th century, most road construction projects were inclined toward solid bitumen, which resulted in more effective asphalt.