Swedish to English Tech/Engineering Transport / Transportation / Shipping Biogas and fermentation t

"För övergång av rälslutningen i anslutning av spårväxlar gäller att utjämningen mellan vertikalt
stående och lutande räl"
This is taken from a procurement document for railway switches and whilst I understand this has something to do with the rail inclination in connection of switches, the part about levelling where 'stående räl' appears has me well and truly stumped.