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OCR for page 215
Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles
E
Fuel Economy and Fuel Consumption as Metrics to Judge the Fuel Efficiency of Vehicles
Figure E-1 shows the relationship of fuel consumption versus fuel economy. The negative slope and the shape of this relationship are both important. The slope of the fuel consumption/fuel economy (FC/FE) curve indicates the amount of change in FC relative to a change in FE. For example, when the slope magnitude in Figure E-1 is high, such as at 10 mpg, there is a large change in FC for a small change in FE. On the other hand, at 50 mpg, there is a small change in FE, since the slope magnitude is very low and approaching zero as indicated by the lower right-hand slope scale on Figure E-1.
FIGURE E-1 Fuel consumption (FC) versus fuel economy (FE) (upper half of figure) and slope of FC/FE curve (lower half of figure). The light-colored lower curve matches the left-hand y-axis, while the dark curve matches the right-hand y-axis.
Fuel consumption decreases slowly after 40 mpg since the slope of the FC/FE curve approaches zero (Figure 2-1 lower curve and right-hand scale). The slope rapidly decreases past 40 mpg since it varies as the inverse of FE squared, which then results in a small decrease in FC for large FE increases. This fact is very important since fuel consumption is the metric in corporate average fuel economy (CAFE) standards for light-duty vehicles. For example, the fuel consumption is 2.5 gallons/100 miles at 40-mpg and 1.25 gallons/100 miles at 80 mpg. Thus, a 40 mpg change in fuel economy results in a change in fuel consumption of only 1.25 gallons/100 miles. In going from 8 to 9 mpg, there is a change in fuel consumption of approximately 1.39 gallons/100 miles. This means that a change from 8 to 9 mpg saves more fuel than a change from 40 to 80 mpg. This nonlinear relationship between fuel economy and fuel consumption has important meaning for regulations, where a reduction in fuel use or in greenhouse emissions is desired. Improving vehicles with high fuel consumption (low mpg) and high vehicle miles traveled (VMT) has much more effect on fuel savings than improving low-consumption (high-mpg) and low-VMT vehicles.
Tables E-1, E-2, and E-3 show vehicle groups and national average payload data that can serve as the basis for National Highway Traffic and Safety Administration (NHTSA) use in determining payloads to be used for testing and simulating any future medium- and heavy-duty vehicle fuel consumption procedures as related to standards. The data in Tables E-1 through E-3 and other data in the report on which the tables are based merit careful study by NHSTA before they are considered for use in a regulation.
OCR for page 216
Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles
The following equations hold for calculating FE and FC:.
The equations above hold from engine on to engine off in order to capture idle time. Chapter 2 refers to an “average payload” to calculate load-specific fuel consumption (LSFC) but does not indicate how to calculate it on a trip delivering cargo. The calculation for average payload is as follows:
where Px = payload in tons carried for time x when the vehicle is moving, and tx = time in hours carrying payload Px. This is a “time average payload” for a vehicle operating in the field and excludes idle time—it is the integral of payload to get the average payload.
From Figure 2.6, LSFC does not decrease significantly for a payload increase as long as the payload is greater than 70 percent of the full payload.
In the equation for payload, if any Px is zero, there is zero in the numerator for that segment, but the time is counted in the denominator, which then lowers the average payload. The FC during the no-load segment would decrease, lowering the total gallons of fuel used. If the time average payload is less than 70 percent of full load, LSFC will increase—if it is greater than 70 percent, LSFC will increase somewhat based on Figure 2.6.
Then,
and the
Therefore,
For picking up cargo, the average payload equation would need a plus payload term for each segment to account for the pickup. Therefore, P2 = P1 − Pd + Pp where Pd = payload delivered and Pp = payload picked up after segment 1,
TABLE E-1 Gross Vehicle Weight Groups
Group
Gross Vehicle Weight (lb)
1
<6,000
2
6,001-10,000
3
10,001-14,000
4
14,001-16,000
5
16,001-19,500
6
19,501-26,000
7
26,001-33,000
8
>33,000
NOTE: Vehicle groups used for average payloads in Tables E-2 and E-3.
SOURCE: Development of Truck Payload Equivalent Factor (TPEF), final report submitted to Office of Freight Management and Operations, Federal Highway Administration, Washington, D.C., by Battelle, 505 King Avenue, Columbus, Ohio 43201. June 15, 2007. Available at http://ops.fhwa.dot.gov/freight/freight_analysis/faf/faf2_reports/reports9/index.htm#toc.
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Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles
TABLE E-2 Average Payload (lb) by Commodities and Gross Vehicle Weight Group VIUS—National
Commodities
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 7
Group 8
Live animals and fish
-
5,055
7,638
5, 424
9,472
17,200
16,345
40, 022
Animal feed or products of animal origin
-
4,682
6,138
3, 760
8,330
11,778
18,980
39, 841
Cereal grains
-
13,348
15,234
8, 690
14,334
17,640
24,208
41, 922
All other agricultural products
-
10,728
6,889
5, 985
7,660
11,348
26,793
34, 616
Basic chemicals
-
*
*
3,386
*
11,180
14,264
38, 431
Fertilizers and fertilizer materials
-
8,062
2,937
5,382
7,898
12,308
25,148
30,134
Pharmaceutical products
-
*
*
-
*
7,455
*
14, 507
All other chemical products
-
2,715
3,046
4, 357
6,193
9,712
17,574
36, 411
Alcoholic beverages
-
-
2,670
-
*
16,177
20,142
35,758
Bakery and milled grains
-
2,000
2,407
7,083
*
3,198
27,732
31,389
Meat, seafood, and their preparation
-
*
10,402
3, 646
-
8,819
10,738
40, 012
Tobacco products
-
-
2,700
-
-
*
9, 253
34, 381
All other prepared foodstuff
-
4,354
3,607
3, 617
5,486
13,240
23,736
38, 894
Logs and other wood in rough
-
5,838
4,880
*
9,384
11,029
22,746
46, 774
Paper and paperboard articles
-
-
*
-
6, 718
8,842
18,591
37, 932
Printed products
-
8,864
3,418
4, 699
2,126
8,578
8, 805
21, 340
Pulp, newsprint, paper, or paperboards
-
*
*
*
-
10,904
15,815
41, 774
Wood products
-
3,303
3,592
5, 410
7,263
8,218
16,182
34, 699
Articles of base metal
*
1,808
2,016
4, 399
4,323
8,095
12,840
29, 564
Base metal finished or semi-finished form
*
3,375
3,871
3, 731
4,080
6,356
12,110
38, 010
Non-metallic mineral products
-
3,737
2,088
3,438
6,652
10,527
28,977
35,962
Non-powered tools
-
2,675
3,167
4, 353
5,421
6,680
9, 899
14, 810
Powered tools
-
3,894
3,602
4, 849
8,513
7,405
12,242
25, 241
Electronic and other electrical equipment
-
2,463
4,068
2, 060
*
7,877
9, 946
26, 353
Furniture, mattresses, lamps, etc.
-
2,056
2,769
2, 591
-
6,397
17,501
22, 598
Machinery
-
4,271
4,277
9, 265
5,020
9,958
17,598
35, 754
Miscellaneous manufactured products
-
1,401
2,411
6, 148
5,615
8,571
17,861
27, 236
Precision instruments and appliances
-
1,455
1,373
10, 095
-
4,391
*
26, 195
Textile, leather, and related articles
-
2,073
2,986
*
8, 701
7,599
41,925
36, 656
Vehicle, including parts
-
3, 751
5,506
5,896
7, 333
8,173
23, 554
31,945
All other transportation equipment
-
-
2,025
5, 431
*
16,312
18,286
42, 517
Coal
-
*
*
-
-
6,748
-
50, 011
Crude petroleum
-
-
-
-
-
8,590
-
39,890
Gravel and crushed stones
-
6,544
6,931
6, 276
10,122
13,770
24,305
39, 130
Metallic ores and concentrates
-
-
*
-
10,000
-
-
42,272
Monumental and building stones
-
*
3,460
5, 782
14,100
10,392
9, 473
35, 960
Natural sand
-
7,306
3,029
12, 849
6,000
11,643
28,662
38, 067
All other nonmetallic minerals
-
7,337
3,064
2,478
7,662
16,262
13,580
38,835
Fuel oils
-
4,484
14,811
-
*
15,422
17,525
39, 634
Gasoline and aviation turbine
-
*
-
2, 825
-
15,128
18,916
53, 423
Plastic and rubber
-
*
2,931
3, 329
*
8,113
12,548
30, 379
All other coal and refined petroleum
-
4,519
4, 336
*
4,874
10, 326
18, 672
41,027
Hazardous waste
-
*
1,500
-
-
6,854
15,517
37, 856
All other waste and scrap
-
3,384
2,927
*
5,951
8,120
12,823
24, 944
Recyclable products
-
3, 153
4,878
3, 689
*
8,425
13,743
27, 532
Mail and courier parcels
*
7,976
5,559
4, 608
7,342
10,884
33,344
31, 628
Empty shipping containers
-
2, 661
*
-
*
2,309
16, 129
26,699
Passengers
-
2,264
2,501
*
*
*
*
*
Mixed freight
-
2,080
2,633
4, 051
*
20,137
28,811
37, 094
Multiple categories
-
3,602
3,375
4, 198
5,463
8,127
17,189
31, 946
Products not classified, blank, not reported or applicable
-
2,471
*
6, 556
7,809
11,622
17,644
30, 545
SOURCE: Development of Truck Payload Equivalent Factor (TPEF), final report submitted to Office of Freight Management and Operations, Federal Highway Administration, Washington, D.C., by Battelle, 505 King Avenue, Columbus, Ohio 43201. June 15, 2007. Available at http://ops.fhwa.dot.gov/freight/freight_analysis/faf/faf2_reports/reports9/index.htm#toc.
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Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles
TABLE E-3 Vehicle Groups and National Average Payload (lb)
Major Body Type
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 7
Group 3
Truck or Truck + Trailer
Bulk
-
6,249
4,798
5,004
10,831
13,152
15,707
30,966
Flatbed
*
4,027
4,767
4,858
7,836
9,465
11,405
16,693
Tank
-
6,077
4,438
7,266
7,249
12,991
15,743
26,858
Van
*
4,179
3,071
4,322
6,770
7,516
9,519
6,233
Reefer
-
4,320
3,196
4,263
*
9,161
10,983
10,414
Logging
-
15,036
*
*
*
10,787
*
42,857
Other
*
2,969
3,075
4,442
5,235
7,391
11,887
23,853
Tractor + Trailer
Automobile
-
-
-
-
*
*
25,443
34,257
Livestock
-
-
-
*
-
44,361
27,747
42,535
Bulk
-
*
-
*
-
36,846
45,319
50,135
Flatbed
-
*
*
*
*
24,997
31,949
41,874
Tank
-
-
-
-
-
*
47,656
49,788
Van
-
-
-
-
-
23,995
28,079
38,721
Reefer
-
-
-
-
-
19,390
24,775
41,426
Logging
-
-
-
*
-
*
*
50,004
Other
-
-
-
-
-
*
31,498
31,800
SOURCE: Development of Truck Payload Equivalent Factor (TPEF), final report submitted to Office of Freight Management and Operations, Federal High-way Administration, Washington, D.C., by Battelle, 505 King Avenue, Columbus, Ohio 43201. June 15, 2007. Available at http://ops.fhwa.dot.gov/freight/freight_analysis/faf/faf2_reports/reports9/index.htm#toc.freight_analysis/faf/faf2_reports/reports9/index.htm#toc.