“…It means that the phase two can start. After it fires, four new tokens are drop into EW_GS_R, EW_TL_G, NS_GS_R, NS_TL_R, respectively, as shown in M 8 : 27) i f p = EW_TL_G(phase2) 1 (R, 30) i f p = NS_GS_R ∅ otherwise in M 9 , transition phase3 is enabled, it can fire. Firing the enabled transition phase3 at marking M 9 yields marking M 10 , it means that the go-straight green lights in north-southward traffic direction turn on and continue for 27 s.…”