An employee of the Department who converts into the Transportation Service shall retain credit for years of service credited by the Department to the employee at the time of conversion. State employees who are hired into the Transportation Service shall receive credit for years of State service. Contractual and temporary employees who are hired into a Transportation Service position shall receive service and leave earning rate credit for the period of their uninterrupted contractual, temporary, or contractual and temporary service which took place immediately before their appointment to a Transportation Service position.