assignment restrictions for the hybrid buses. As shown in Table 6, bus operations from Mother Clara Hale Depot for 40-foot standard buses had an overall average speed of 6.52 mph in 2004 and 6.13 mph in 2005 (this reduction in average speed was the result of a high-speed route being moved to another depot).
Both depots showed a general downward trend in average speed from 2004 to 2005. Much of these decreases in average speed are likely caused by an increase in congestion on the routes and some changes in NYCT’s bus scheduling. Average speeds for the West Farms and Mother Clara Hale depots appear to be similar and comparable. Total mileage differences are caused by the number of buses assigned to the depots (250 buses at West Farms and 125 buses at Mother Clara Hale).
Bus use is intended as an indicator of reliability and availability for bus service. The lack of bus usage may be an indication of downtime for maintenance or purposeful reduction of planned work for the buses.
Table 7 shows average monthly mileage per bus for the evaluation period for the diesel and CNG buses at West Farms. Figure 13 shows cumulative average monthly miles per bus. The CNG buses had an average of 2,244 miles per bus and the diesel buses had an average of 1,952 miles per bus. The evaluation period for the CNG buses was eight months; the diesel bus evaluation period was 12 months. However, most of the diesel buses have fewer than 12 months used because of in-chassis rebuilds of the engines. The usage of the CNG buses was significantly higher (overall 15% higher) than the diesel buses during most of the evaluation period. This occurred because of the age of the diesel buses and the cost of operation. NYCT tends to operate the more cost effective buses, which are typically the newer ones.
Table 6. Average Speed for Al
l Standard Buses (40-foot) at Mother Clara Hale
Day of Week
Table 8 shows average monthly mileage per bus for the diesel and hybrid buses at Mother Clara Hale Depot. Figure 14 shows the average monthly miles per bus for the hybrid and diesel buses. The hybrid buses showed an average of 2,461 miles per bus; the diesel buses had an average of 2,385 miles per bus. By the end of the evaluation period shown, these two fleets were being used at essentially the same rate.
The CNG and hybrid buses also have similar usage rates with the hybrid bus usage about 10% higher than the CNG buses.