Performance Grade (PG) Bitumen is bitumen which is graded based on its performance at different temperatures. The main purpose of grading and selecting asphalt binder using the PG system is to make certain that the binder has the appropriate properties for environmental conditions in the field. PG asphalt binders are selected to meet expected climatic conditions as well as traffic speed and volume adjustments. Therefore, the PG system uses a common set of tests to measure physical properties of the binder that can be directly related to field performance of the pavement at its service temperatures by engineering principles. The PG grading system is defined by two numbers, which represent pavement temperatures. The first number PG 64-XX represents the high pavement temperature in degrees Celsius, while the second number PG 64-XX represents the low pavement temperature which is minus. Notice that these numbers are pavement temperatures and not air temperatures.