Dimensional Model for inheritance in dimensions
While in a traditional OLTP system you may need to be concerned about normalizing and inheritance, in a typical data warehouse system you will want to denormalize to accelerate query responses.

In this case, I would design an Employee_Dimension table which had all relevant columns about an employee which you might want to query against, along with an additional column which I might call employee_role, which I would fill in with entries like Driver, Manager, etc. and then have another column which had either the truck_number filled for employees who were a driver, or leave the column as NULL when they aren't drivers. Of course, you can add even further columns to include information for other employee roles.

Long story short, if you're building a typical star schema, you can achieve faster query results by using heavy denormalization, at the cost of storage space of course.