Biolock

The Biometric Lock (biolock) is a system that prevents unauthorized people from entering and taking over a vehicle they do not own or have access to. It has multiple settings for levels of security and is linked with the people management interface. It can be accessed on the manifest by selecting the vehicle you are currently piloting and pressing shift+b(use shift+up/down arrow to scroll the manifest)

Options are:
0 - unlocked
1 - no enemies
2 - allies
3 - partners
4 - owner

As one would expect the level selected also allows higher levels, for example selecting level 2 will allow allies, partners and the owner to enter the vehicle.
The biolock can be picked with the (biometric) lock pick kit