This is the (more or less) situation right now.
Here you can see the rail lines.
Notice how in Volnovakha area, the ONLY rail line down south towards crimea is only a MILE away from the areas controlled by Ukraine.
The battle lines are somewhere between Solodke (Ukrainian) and Berezove (russian). That's the bottle neck for rail transit.
The rail line is right in the middle. Currently in possession of russians, but... only a mile from Ukies.
Yeah, the Ukrainians can destroy that rail line any time they want. That will cripple russian military shipments to Crimea, and it will be super hard to repair unre constant ukrainian bombardment.
If you are in Crimea and are thinking about getting the fuck out of dodge, these are about the last moments to do so. Soon, you won't be able to.