Source: FHWA Highway Traffic Noise Prediction Model (FHWA-RD-77-108)

National Reference Energy Mean Emission Levels as a Function of Speed

Legend:
  1. AUTOMOBILES: ALL VEHICLES WITH TWO AXLES AND FOUR WHEELS
  2. MEDIUM TRUCKS: ALL VEHICLES WITH TWO AXLES AND SIX WHEELS
  3. HEAVY TRUCKS: ALL VEHICLES WITH THREE OR MORE AXLES