Development and Evaluation of a Simplified Version of MOVES for - PowerPoint PPT Presentation

Development and Evaluation of a Simplified Version of MOVES for Coupling with a Traffic Simulation Model Bin Liu and H. Christopher Frey Dept. of Civil, Construction, and Environmental Engineering North Carolina State University, Raleigh, North Carolina 27695 Prepared for: 105th Annual Meeting of the Air & Waste Management Association San Antonio, Texas June 20, 2012

Motivation • The U.S. EPA Motor Vehicle Emission Simulator (MOVES) is a computationally and data intensive model for estimating vehicle emission factors.

Motivation • Traffic Simulation Models (TSMs) quantify the effect of infrastructure design and traffic control measures (TCMs) on vehicle dynamics (i.e. speed and acceleration of individual vehicles). vs.

Motivation • Because TSMs typically simulate only a few hours of vehicle activity, it is not necessary to dynamically simulate the effect of constant factors such as fuel properties and inspection/maintenance programs. Vehicle Dynamics Vehicle Fleet MOVES I/M programs Fuel properties (others)…

Motivation • Because TSMs typically simulate only a few hours of vehicle activity, it is not necessary to dynamically simulate the effect of constant factors such as fuel properties and inspection/maintenance programs. Vehicle Dynamics Vehicle Fleet MOVES I/M programs Constants Fuel properties (others)…

Motivation • A simplified emission model is needed for incorporation into TSMs. The simplified model should accurately estimate fleet average emission rates while accounting for individual vehicle speed profiles.

Objectives • Develop a simplified MOVES model that can be efficiently coupled with TSMs. • Evaluate the accuracy of the simplified model. • Evaluate the sensitivity of the simplified model to variations in driving cycles.

Conceptual Model • Conceptual Model : 𝐹𝐹 𝐷 = 𝐹𝐹 𝑐 × 𝑇𝑇𝐹 𝐷 (1) EF c = emission factor for driving cycle c, g/mi EF b = emission factor for base cycle b, g/mi SCF c = speed correction factor for driving cycle c

Calibration of Base Emission Rate Emission rate for a base cycle estimated by MOVES 𝐹𝐹 𝐷 = 𝐹𝐹 𝑐 × 𝑇𝑇𝐹 𝐷 (1) EF c = emission factor for driving cycle c, g/mi EF b = emission factor for base cycle b, g/mi SCF c = speed correction factor for driving cycle c

Speed Correction Factor SCF for any arbitrary cycle c calculated by Eq. 2 𝐹𝐹 𝐷 = 𝐹𝐹 𝑐 × 𝑇𝑇𝐹 𝐷 (1) EF c = emission factor for driving cycle c, g/mi EF b = emission factor for base cycle b, g/mi SCF c = speed correction factor for driving cycle c

Estimating the Speed Correction Factor 𝑑 ∑ 𝑤 𝑐 𝐹𝐹 𝑛 × 𝑔 𝑛 𝑛 𝑇𝑇𝐹 𝐷 = 𝑤 𝑑 (2) 𝑐 ∑ 𝐹𝐹 𝑛 × 𝑔 𝑛 𝑛 SCF c = speed correction factor for driving cycle c ER m = emission rate for OpMode m in MOVES default database, g/hour c = fraction of time in OpMode m for cycle c f m b = fraction of time in OpMode m for base cycle b f m v b = cycle average speed for base cycle b, mph v c = cycle average speed for cycle c, mph

Case Study • Passenger Cars, 5 years old, Gasoline • 18 MOVES default driving cycles. Average speeds of 2.5 mph to 76 mph • Base Cycle: Federal Test Procedure (FTP) • Scenario Assumptions: –Ambient Temperature: 65 o F –Gasoline for light duty vehicles, diesel for others • Estimate cycle average emission factors using simplified model • Evaluate the accuracy of the simplified model compared to MOVES results

Definition of MOVES Operating Mode Bins by Speed and VSP Ranges 0 mph< v i ≤ 25 mph 25 mph < v i ≤ 50 mph v i >50 mph OpMode OpMode OpMode Description Description Description ID ID ID 11 VSP< 0 21 VSP< 0 12 0≤VSP< 3 22 0≤VSP< 3 13 3≤VSP< 6 23 3≤VSP< 6 33 VSP< 6 14 6≤VSP< 9 24 6≤VSP< 9 35 6≤VSP<12 15 9≤VSP<12 25 9≤VSP<12 16 12≤VSP 27 12≤VSP<18 37 12≤VSP<18 Other: 28 18≤VSP<24 38 18≤VSP<24 0 Braking 29 24≤VSP<30 39 24≤VSP<30 1 Idling 30 30≤VSP 40 30≤VSP v i : instantaneous speed of the i th second

Emission Rates for Operating Mode Bins in MOVES Default Database: 5 yr old Passenger Cars Speed Range 60 35 0< v i ≤ 25mph 25< v i ≤ 50mph CO 2 Emission Rate (kg/hr) v i > 50 mph NO x Emission Rate (g/hr) 30 50 CO2 25 40 NOx 20 30 15 20 Braking 10 Idle 10 5 0 0 0 1 11 12 13 14 15 16 21 22 23 24 25 27 28 29 30 33 35 37 38 39 40 Operating Mode Bins

Speed and Vehicle Specific Power (VSP) for Federal Test Procedure (FTP) 90 30 Speed VSP 80 20 70 10 Speed (mph) 60 0 VSP (kw/ton) -10 50 40 -20 30 -30 20 -40 10 -50 0 -60 0 300 600 900 1200 1500 1800 Time (second)

Speed Correction Factors for 18 Driving Cycles 6 CO2 NOX Speed Correction Factor 5 CO HC 4 3 2 1 0 0 10 20 30 40 50 60 70 80 Average Speed (mph)

Speed Correction Factors for CO 2 6 Speed Correction Factor 5 4 3 2 1 0 0 10 20 30 40 50 60 70 80 Average Speed (mph)

Speed Correction Factors for NO x 6 Speed Correction Factor 5 4 3 2 1 0 0 10 20 30 40 50 60 70 80 Average Speed (mph)

Speed Correction Factors for CO 6 Speed Correction Factor 5 4 3 2 1 0 0 10 20 30 40 50 60 70 80 Average Speed (mph)

Speed Correction Factors for Hydrocarbons 6 Speed Correction Factor 5 4 3 2 1 0 0 10 20 30 40 50 60 70 80 Average Speed (mph)

Different Emission Rates for Cycles with Similar Average Speeds 6 CO2 NOX Speed Correction Factor Cycle Speed CO 2 NO x CO HC 5 CO HC (mph) (g/mi) (g/mi) (g/mi) (g/mi) 153 30.5 346 0.069 1.8 0.009 4 1029 31.0 351 0.081 2.1 0.011 3 Diff: 2% 1% 17% 18% 32% 2 1 0 0 10 20 30 40 50 60 70 80 Average Speed (mph)

Comparing Simplified Model and MOVES Cycle CO 2 NO x Ave. Simplified Simplified MOVES % Diff. MOVES Speed Model Model % Diff. (g/mi) (mg/mi) (mph) (g/mi) (mg/mi) 2.5 1930 1930 0.35 39 39 0.39 30.5 347 347 - 0.01 28 28 0.02 46.1 319 319 0.03 36 36 0.04 66.4 308 308 - 0.05 47 47 0.00 73.8 323 323 - 0.06 60 60 - 0.14

Errors of the Simplified Model 4% CO2 NOX CO 2 NO x Percent Difference 2% CO HC 0% -2% -4% 0 10 20 30 40 50 60 70 80 Average Speed (mph)

Average of Errors of the Simplified Model Average Percent Error: Simplified vs. MOVES Models, All Selected Cycles CO 2 NO x CO HC Vehicle Types Passenger Car (PC) 0.02 0.03 0.02 0.04 Passenger Truck (PT) 0.01 -0.22 -0.07 0.17 Light Commercial Truck (LCT) 0.46 -0.35 0.28 -0.09 Single Unit Short Haul Truck (SHT) -0.35 -0.43 -0.11 -0.09 Combination Long Haul Truck (LHT) 0.06 -0.41 0.06 0.20 18 driving cycles each for PC, PT, and LCT 11 driving cycles each for SHT and LHT. These five vehicle types comprise more than 95% of the fleet.

Conclusions • The simplified model is accurate and precise. – Wide range of average speed – Vehicle types – Pollutants • The simplified model is sensitive to driving cycles. – Cycle average speed – Specific driving cycles

Conclusions • In future, the simplified model will be applied for a fleet of vehicles of mixed types and ages, and coupled with a TSM.

Acknowledgements • Although the research described here has been funded wholly or in part by the U.S. Environmental Protection Agency's STAR program through EPA Assistance ID No. RD-83455001, it has not been subjected to any EPA review and therefore does not necessarily reflect the views of the Agency, and no official endorsement should be inferred. • Student travel support for this meeting provided by Research Triangle Park (RTP) Chapter and South Atlantic States Section (SASS) of A&WMA.

Definition of Braking and Idling • Braking: a t ≤ - 2.0 OR (a t ≤ - 1.0 AND a t-1 ≤ - 1.0 AND a t-2 ≤ - 1.0) a t = acceleration at t th second, mi/hr - sec. • Idling: -1.0 ≤ v t < 1.0 v t = speed at t th second, mph.