7.   The Consultants' Study
          An Engineer's Commentary on Operating Costs

The following is a sample of a variance analysis on the cost per kilometre figures for trolleybuses vs. diesels that are presented in the Booz Allen Hamilton study. A variance analysis should be part of any thorough study. The fact that the Booz Allen Hamilton report did not perform such analyses suggests its conclusions regarding future costs cannot be taken as facts, but rather as opinions based on one set of assumptions. The analysis below is merely intended to show that very different figures could reasonably be adduced based on the same base data contained in the Booz Allen Hamilton report. Other variants are certainly possible.

The Report includes the following diagram comparing trolley and diesel bus cost/km figures:

The Report asserts that "The trolley system has been -- and will continue to be -- more expensive to operate and maintain than equivalent diesel service". The analysis below attempts to bring out that the Report's analysis of even current costs is biased because it does not compare like with like [it buries significant detail in fleet averages] and that its prediction about future costs favouring diesels is based on a set of assumptions that may well be wrong.

Current cost/km data as per diagram as above:

Plotting this data:-

Current cost/km data as per diagram as above but with adjustments listed below/overleaf:-

Diesel Maintenance up lift = 30%
Diesel fuel uplift = 69%
Trolley maintenance reduction = -50%

Plotting this data shows that modest and reasonable changes to the data more fairly representing diesel and [new] trolley comparisons shows trolleybuses as coming out slightly ahead of diesel on running costs at 95 % utilisation [many other systems achieve very close to 100% so 95% should be readily achievable].

Looking to the future meeting exceedingly stringent post 2007 emission targets may require diesel electric hybrid technology. Such vehicles are likely to cost as much as trolleybuses but incur much higher maintenance costs than current diesels because of the need to frequently replace batteries. Fuel consumption may be modestly less, although in the long-term fuel costs are certain to rise. Recalculating the above figures to reflect this gives:-

Battery replacement costs per km based on available data = $0.35

Plotting this data shows that post 2007 diesels could have no capital cost advantage over trolleybuses but yet have very much higher running costs.

It should not be assumed that trolleybus utilisation cannot exceed 100%. The 100% figure above represents all current scheduled trolleybuses journeys being worked by trolleybuses i.e. no diesel substitution. If the number of scheduled trolleybus journeys is increased, this would raise trolleybus utilisation beyond 100% and further improve trolleybus costs relative to diesel. Potentially perhaps, future trolleybus operating costs could be half those of future diesel. Retaining the trolleybus system would be a very prudent decision.