How can you enforce dual control access to the vault with only three people?

I'm not sure of your question.

Dual control requires 2 people - you have 3

I think bsf means there may only be three employees at that location. We have a location like that; however we allow one person to enter the vault by themselves. Is this ideal? Heck no, but it's all we can do at the moment.

Dual control does not mean 2 people involved in a process. Dual controls means 2 people with opposite controls involved in a process.

More and more banks have vaults under sole control of one employee. Especially ones with small staffs. In the event, a vault is accessed by some one other than it is assigned. It should then be accessed under dual control.

We have locations with most days only 2 people and make dual control work.