761—820.1 (327G) Definitions. The following terms when used in this chapter of rules shall have the following meanings:
AAR signal unit.  The relative maintenance difficulty value assigned to component parts of an active warning device. Units and interpretations are designated by the Association of American Railroads Signal Manual, Part 203 (1984).
Active warning devices. Traffic control devices activated by the approach or presence of a train, such as flashing light signals, flashing light signals with cantilever assemblies, and flashing light signals with automatic gate arms, all of which actively warn motorists of a train.
Maintenance costs of active warning devices. Costs incurred by a railroad associated with the repair or replacement of obsolete, worn out, damaged, or missing component parts of an approved active warning device. Maintenance costs shall include repair or replacement of damaged, vandalized, or stolen component parts only for that amount which exceeds the amount recovered from the liable party or the liable party’s insurer.
Safety fund. The highway grade crossing safety fund established in Iowa Code section 327G.19, and administered by the department.