You have now decided the basic specification for the vehicles and maybe fuel type and engine size. Now you need to establish how many are needed.

What are the business plans over the next three years or more?

Speak to business managers and other stakeholders. Don't assume that the current business model will be in place going forward.

Will the business be expanding - or downsizing?

A rapid expansion or new acquisition may see increased demands from new employees. Will the vehicles selected be able to meet this demand or are there likely to be supply issues?

Will the company cover a larger geographic area or are sales territories going to change?

This could create a need for higher or lower mileages and hence affect the diesel/petrol/alternative fuel decision.