. ▁If ▁this ▁crossing ▁time ▁is ▁constant ▁across ▁a ▁network , ▁connecting ▁times ▁between ▁lines ▁are ▁kept ▁consistent ▁in ▁both ▁directions . ▁ ▁At ▁the ▁symmetry ▁time , ▁the ▁tim et able ▁is ▁mirror ed ▁in ▁both ▁directions . ▁At ▁the ▁ends ▁of ▁the ▁line , ▁the ▁center ▁of ▁the ▁turn around ▁time ▁coinc ides ▁with ▁the ▁symmetry ▁minute . ▁The ▁distance ▁between ▁two ▁consecutive ▁symmetry ▁times ▁is ▁equal ▁to ▁half ▁the ▁cycle ▁time , ▁so ▁on ▁an ▁hour ly ▁schedule , ▁opposite ▁trains ▁on ▁the ▁same ▁line ▁cross ▁every ▁ 3 0 ▁minutes . ▁On ▁a ▁two - hour ▁cycle , ▁there ▁is ▁a ▁symmetry ▁time ▁every ▁hour . ▁ ▁In ▁principle , ▁a ▁train - enc ounter ▁can ▁be ▁set ▁at ▁any ▁time . ▁However , ▁at ▁the ▁transition ▁between ▁two ▁networks ▁or ▁lines , ▁it ▁is ▁exped ient ▁to ▁set ▁uniform ▁symmetry ▁minutes , ▁to ▁create ▁a ▁symmet rical ▁connection ▁relation . ▁For ▁the ▁long - distance ▁cycle ▁systems ▁of ▁Ö BB ▁and ▁S BB , ▁the ▁Forsch ungs gesellschaft ▁für ▁Straßen - ▁und ▁Verkehr sw esen ▁für ▁Deutschland ▁( Res earch ▁Association ▁for ▁Ro ads ▁and ▁Tra ffic ▁for ▁Germany ) ▁recomm ends ▁minute ▁ 5 8 , ▁so ▁a ▁four - min ute ▁minimum ▁connecting ▁time ▁results ▁in ▁a ▁departure ▁at ▁minute ▁ 0 . ▁Meanwhile , ▁most ▁rail ways ▁in ▁Central ▁Europe ▁and ▁a ▁number ▁of ▁other ▁transport ▁operators ▁have ▁established ▁the ▁symmetry ▁minute ▁ 5 8 ½ , ▁for ▁a ▁three - min ute ▁hold ▁time