BUSINESS CASE FOR COMPRESSED NATURAL GAS IN MUNICIPAL FLEETS - Natural Gas-powered Cars and Trucks: Options and Issues - page 57

Table 1. Seven Modeled Fleets and Their Parameters

Scenario Fleet Type Avg.

VMT

FE Diesel
(mpg)

FE CNG
(mpDGE)

Incremental
Cost

Vehicle
Life

1 Transit Buses 35,286 3.27 3.02 $50,502 15

2 School Buses 12,000 7.00 6.13 $31,376 15

3 Refuse Trucks 25,000 2.80 2.51 $30,295 12

1/2 Transit, 1/2
School

4 23,643 5.14 4.57 $40,939 15

1/2 Transit, 1/2
Refuse

5 30,143 3.04 2.76 $40,399 14

1/2 School, 1/2
Refuse

6 18,500 4.90 4.32 $30,836 14

7 1/3 Each 24,095 4.36 3.88 $37,391 14

The parameters for the combination fleets (scenarios 4 through 7) are
weighted averages according to their composition by the first three fleets.
Parameters for the first three fleets are listed below.
Transit Buses
•

The average vehicle-miles traveled (VMT) of transit buses is 35,286
miles/year derived from tables 8 and 9 in American Public Transit
Association (APTA) 2009.

• The average fuel economy of diesel buses in the United States is 3.27

mpg, which is calculated from tables 8, 9, and 12 in APTA 2009.

• The average fuel economy of CNG buses is 3.02 miles per DGE

(mpDGE), which is calculated from tables 8, 9, and 15 in APTA
2009.

• Incremental cost ($50,502) is an average of the incremental costs

found in Chandler et al. 2006 (Table 6 adjusted for inflation) and from
an interview with Bob Antila (Antila 2009).

• Bus lifetime (15 years) is the average retirement age of buses as

reported in table ES-2 in the Federal Transit Administration's study on
the useful life of buses (FTA 2007).

School Buses
• Average VMT of a school bus is 12,000 miles/year (American School

Bus Council 2009).

• Average fuel economy of a diesel school bus is 7 mpg (American

School Bus Council 2009 and Andre 2009).