When I first started playing this would happen continuously in electro - zeds would never, ever give up so you'd have these gigantic trains of zeds going around electro.
Worst part was -when you saw one heading your way - what could you do? If you shoot the train driver, the train just piles onto you. If you tried to shoot the zombies well not enough ammo usually for 40+ zeds. if you ried to hide and the train driver saw you -all they had to do was run past you and some would peel onto you. If you tried to run you'd have your own train.
Was fairly frustrating and made me not go to electro for many weeks.
Now I love electro - nice place. Good times, good people.