Assignments instead of a shared account
Each user should have their own account. The administrator assigns the vehicles they actually use. This identifies the author of each record and allows access to be revoked quickly without changing other people's passwords.
The administrator approves
The driver records the trip and enters odometer readings. The administrator sees drafts, resolves conflicts and approves the report. Billing documents and maps remain outside the driver's role.
Changing vehicles during the day
An assignment may apply for a specified period. This prevents the system from suggesting a vehicle the employee can no longer access.