Study of the Driving Cycle for Heavy Duty Trucks in Hilly Terrain and Its Effect on Calculated Emissions, and Comparison of Two Mobile Emission Models

Vehicle emissions were estimated using MOVES2010a and MOBILE6.2 for a Pittsburgh case study involving a modal shift in freight transportion. MOVES2010a (hereafter referred to as MOVES) is currently the USEPA official mobile source emissions computer model; it replaced the older model, MOBILE6.2. Changing the method of hauling freight from highway to waterway is the transport modal shift. Results from this part of the study showed that emission estimates for all vehicle types using MOVES were higher than emissions estimated using MOBILE6.2/NMIM for CO, NO_X, PM₁₀, PM_2.5, and VOC, but emissions were lower for CO₂ and NH₃ using MOVES relative to MOBILE6.2. For heavy-heavy duty diesel (HHDD) vehicles, higher emissions were estimated using MOVES for all pollutants except for NH₃ when compared to MOBILE6.2. The largest difference between the two models was seen in PM₁₀ and PM_2.5.

The second part of this dissertation focused on driving cycles for HHDD vehicles in hilly terrain and its effect on emissions. The MOVES model incorporates 12 default driving schedules for HHDD vehicles. Each driving schedule represents different average vehicle speeds, which tend to over generalize the driving patterns for these vehicles in hilly terrain. The characteristics of HHDD vehicle driving cycles were analyzed by using actual GPS speed and terrain data from driving activity that occurred on a section of the Federal Interstate to demonstrate possible drawbacks of default driving schedules in the current version of MOVES. Profiles of speed versus time as well as road grades were constructed to validate this. Emissions were calculated using a MOVES’ operating mode approach. Results showed that a wider range of speeds and higher scaled tractive power occurred in the driving cycles constructed from the real activity data in hilly terrain than the MOVES default driving schedules. NO_X, PM_2.5, and THC emissions and total energy consumption calculated using the synthetic driving cycles of the trucks with grades, associated with the hilly terrain, were 7.6%, 14%, 3%, and 11%, respectively, higher than when using the MOVES default driving schedules at the same average speed (63.9 mph) for 0.3% average road grade. On the other hand, CO emissions were 3.4% lower for the synthetic driving cycles. More analyses associated with the driving cycles were presented in this dissertation, and recommendations were made regarding an improvement of default driving schedules in MOVES as well.