A spare vehicle and spare containers do not solve the same failure. A container cannot provide transport when a vehicle is unavailable; a unit failure may not require another vehicle. Base the choice on incident records.

Keep an incident log

Record date, cause, start and end, affected route and delayed deliveries. Code vehicle, refrigeration unit, demand spike and clean-container shortages separately.

For a vehicle, total rental or capital, insurance and maintenance. For containers, add purchase, cleaning, storage, return, loss and coolant preparation. Compare the same period and route demand.

For a container pool, measure turnaround, ready-container count and product-temperature performance. Recalculate as incidents and delivery records change.