NYCT’s CNG cost is based on two components—the commodity price of the natural gas from the pipeline and the Trillium add-on to pay for the station operation. Over the evaluation period, this has been $0.96 per therm for the natural gas and $0.24 per therm for Trillium, which results in a total cost of $1.32 per therm or $1.78 per diesel equivalent gallon.
When compared to the diesel baseline study group, the fuel cost per mile for the CNG buses was $1.04 per mile for CNG and $0.75 per mile for diesel—39% higher for CNG at West Farms Depot. The hybrid buses were 31% lower than their diesel baseline study group at $0.72 per mile for diesel and $0.49 per mile for hybrid buses at Mother Clara Hale Depot. Across the depots, the CNG buses have a fuel cost per mile 53% higher than the hybrid buses.
The maintenance analysis in this section only includes the CNG and hybrid buses. The diesel baseline buses at the two depots are much older and have much higher maintenance costs. The CNG and hybrid buses are new enough that they have much of the expensive maintenance done under warranty by the manufacturers and their distributor mechanics. When possible, this warranty maintenance cost is captured and provided in the report, but is not included in the maintenance cost analysis. All of the comparisons in this section are hybrid buses compared to CNG buses as the baseline.
Both the CNG and hybrid buses are similar in age and the maintenance costs have been collected in a similar way for each study group. The duty cycle and maintenance practices at West Farms and Mother Clara Hale depots are similar and do allow a comparison between the CNG and hybrid buses. These buses are the same model (Orion VII) and have been in service about the same amount of time.
For the CNG and hybrid buses, maintenance data were collected from the start of operations. All work orders and parts information available were collected for the study buses. The maintenance analysis discussions include only maintenance data from the evaluation period of October 2004 through May 2005.
Total Maintenance Costs Total maintenance costs include the costs of parts and hourly labor costs of $50 per hour, and do not include warranty costs. Cost per mile is calculated as follows:
Cost per mile = ((labor hours * 50) + parts cost)/mileage
The labor rate has been artificially set at a constant rate of $50 per hour so that others can change this rate to one more similar to their own. Also, this rate does not reflect NYCT’s current hourly mechanic rate.
Table 11 shows total maintenance costs for the CNG buses at West Farms Depot and Hybrid buses at Mother Clara Hale Depot. Two of the CNG buses had higher total maintenance costs than the other eight CNG buses. These higher costs were caused mostly by brake reline activities. There were two hybrid buses (buses 6367 and 6379) that had total maintenance costs