  Runway incursions are among the most serious safety concerns in air traffic
control. Traditional A-SMGCS level 2 safety systems detect runway incursions
with the help of surveillance information only. In the context of SESAR,
complementary safety systems are emerging that also use other information in
addition to surveillance, and that aim at warning about potential runway
incursions at earlier points in time. One such system is "conflicting ATC
clearances", which processes the clearances entered by the air traffic
controller into an electronic flight strips system and cross-checks them for
potentially dangerous inconsistencies. The cross-checking logic may be
implemented directly based on the clearances and on surveillance data, but this
is cumbersome. We present an approach that instead uses ground routes as an
intermediate layer, thereby simplifying the core safety logic.
