Comparison of on-road emissions for hybrid and regular transit buses

Figures & data

Table 1. Comparison of hybrid versus regular buses over various test cycles

	Test Cycle
Pollutant	CBD	NYBC	Manhattan	OCTA	KCM	UDDS
CO2	−19% ^a	−40% ^a	−33% ^a	−35% ^d	−24% ^d
	−37%^b		−44^d
	−38%^c
	+35%^d
CO	−97%^a	−56%^a	−98%^a	−32%^d	−60%^d	−47%^e
	−94%^b		NS^d	−82%^e
	−38%^c		−73%^e
	−48%^d
	−72%^e
NOx	−36%^a	−44%^a	−44%^a	−29%^d	−18%^d	−60%^e
	−49%^b		−39%^d	−42%^e
	−49%^c		−52%^e
	−27%^d
	−45%^e
HC	−43%^a	+88%^a	−28%^a	NS^d	−56%^d
	+120%^b		NS^d
	+450%^c
	−75%^d
PM	−50%^a	−77%^a	−99%^a	−51%^d	NS^d	approx. −90%^e
	−93%^b		−93^d	approx.
	−60%^c		approx. −90%^e	−90%^e
	−97%^d
	approx. −90%^e
Notes: NS = no statistically significant difference. ^a Chandler et al. (2002). ^bCompared with diesel bus without catalyzed DPF (Battelle, 2002). ^cCompared with diesel bus with catalyzed DPF (Battelle, 2002). ^dChandler and Walkowicz (2006). ^e Wayne et al. (2004).

Table 2. Specifications of both hybrid diesel buses and conventional diesel buses

Specification	Hybrid Diesel Buses	Conventional Diesel Buses
Engine year	2010	2010
Capital cost	$521,970	$367,115
Manufacture	Gillis Hybrid	Gillig
Bus type	Low floor	Low floor
Engine	Cummins '10 ISL 280 HP,in line six cylinders	Cummins '10 ISL 280 HP,in line six cylinders
Transmission	Voith DIWA Parallel Hybrid	Voith D864.5 4-speed
Aftertreatment	Particulate filter (CPF)	Particulate filter (CPF)
Governed speed	65 mph	65 mph
Start date	June 28, 2010	June 28, 2010
Frontal area	113.5 × 102 ft	113.5 × 102 ft
Length × Height	40 ft × 138 in	40 ft × 138 in
Curb weight	29,500 lbs	25,000 lbs

Table 3. Route characteristics

Route	Miles	Fraction of Route
Urban arterial 35 mph	5.08	32.2%
Urban arterial 40 mph	0.54	3.4%
Residential 30 mph	6.22	39.5%
Residential 25 mph	1.79	11.4%
Campus 25 mph	2.13	13.5%
Total route	15.8

Table 4. Speed ranges for route

Speed Range	Average Percent of Trip
0	43%
>0 to <10	13%
10 to <20	20%
20 to <30	19%
30 to <40	4%

Table 5. Bins used to evaluate bus emissions by VSP range

Bin	VSP Range (kW/metric ton)
lower than −10	VSP < −10.5
−10 to 0	−10.5 ≤ VSP < 0
0	0 ≤ VSP < 0.5
1–2	0.5 ≤ VSP < 2.5
3–4	2.5 ≤ VSP < 4.5
5–6	4.5 ≤ VSP < 6.5
7–8	6.5 ≤ VSP < 8.5
9–10	8.5 ≤ VSP < 10.5
11+	11.5 ≤ VSP

Figure 1. CO₂ emissions by VSP bin and bus type.

Figure 2. CO emissions by VSP bin and bus type.

Figure 3. HC emissions by VSP bin and bus type.

Figure 4. NO_x emissions by VSP bin and bus type.

Chandler , K. , Walkowicz , K. and Eudy , L. 2002 . New York City Transit Diesel Hybrid-Electric Buses: Final Results. DOE/NREL Transit Bus Evaluation Project National Renewable Energy Laboratory

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Battelle . 2002 . Technical Assessment of Advanced Transit Bus Propulsion Systems , Columbus , OH : Battelle . For the Dallas Area Rapid Transit, Dallas, Texas.

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Chandler , K. , and , K. and Walkowicz . 2006 . King County Metro Transit Hybrid Articulated Buses: Final Evaluation Report , . NREL/TP-540-40585. : National Renewable Energy Laboratory .

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Wayne , W.S. , Clark , N.N. , Nine , R.D. and Elefante , D. 2004 . A comparison of emissions and fuel economy from hybrid-electric and conventional-drive transit buses . Energy Fuels , 18 : 257 – 270 . doi: 10.1021/ef030096t

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