First, FTA’s 20% spare ratio requirement applies to fleets of 50 or more fixed route buses. Smaller fleets do not have a fixed percentage, but the ratio should be reasonable.
Second, the spare ratio requirement applies at the time of a grant application to ensure the buses to be procured are needed. If an agency anticipates that it may temporarily (up to 2 years) deviate from the spare ratio requirement with the purchase of new vehicles, it can seek approval for the deviation from its FTA Regional office.
Third, if an agency needs more electric buses operating than diesel buses during its peak service, -that becomes its new base. For example, if previously a grantee had 100 diesel buses operating in maximum fixed route service, it could have 20 spares for a total of 120 buses. If it needs 110 electric buses operating in maximum fixed route service, it can have 22 spares, for a total of 132 buses.
Finally, FTA permits grantees to retain vehicles that have met their useful life in contingency fleets, which do not count towards a grantee’s spare ratio. Contingency fleets are permitted for emergency use and specifically for the introduction of zero-emission vehicles.
See
FTA’s Spare Ratio page for additional FAQs.