I can recall in days long long ago, when I was taken to Chester and Liverpool to visit the Northern side of my family,and there was no loop via Moorfields and Lime Street, that Central Station "Low Level?" was an island platform, with a grand staircase leading down from the ticket area and at the platform level, there was a sliding grille that the "platform managers" used to close to prevent the overcrowding of the island platform.
I don't know if it were possible to close of the ticket barriers (if there are any) to prevent over-crowding on the platforms these days.
By the way, I used to love watching the empty trains, pass out of the station to reverse and come back onto the other side of the island platform. I really wanted to ride on the empty train and come back again. I am talking of 1962 when I was 9 years old, and the trains ran to New Brighton, West Kirby and Rock Ferry, with 6 coaches, and on the platform was a Newspaper, cigarette and sweets kiosk in the centre of the island, and I was given a box (not a tube) of Fruit Gums by my favourite uncle. (joyous).