The emergency measure applies to all 55 Tangara trains in the fleet, meaning those travelling over the grand final weekend will be affected. The policy was already in place on selected services, but has now been applied fleet-wide.
Train surfing or "buffer riding" has been a persistent problem on the Tangaras, fuelled by social media videos where riders boast of their exploits. The fleet's lack of CCTV has made the trains especially vulnerable to vandalism, according to Transport Minister John Graham.
To discourage the practice, Sydney Trains has fitted slanted "nose cones" to the buffers on all Tangaras, removing the flat surface that allowed surfers to jump onto the rear of the train. Mr Graham said the measures had worked: on the T4 Eastern Suburbs and Illawarra line, there were just three incidents between July and September, compared with 127 cases of buffer riding in the previous 12 months.
"Those cones have made a big difference," Mr Graham said. He described locking the rear carriages as a "pragmatic step" needed to ensure the trains run on time. "It's one we don't want to take, but reliability is our number one focus."
However, Shadow NSW Transport Minister Natalie Ward said the government had effectively surrendered to vandals and train surfers. "It can't be 'lights out' for commuters. You can't give up on this. Transport policy has to be commuters first, dropkicks second," she said.
Rail, Tram and Bus Union secretary Toby Warnes said the internal door to the crew cab was being repeatedly targeted. He said he had seen the social media videos himself.
More than two years have passed since the government announced a $447 million program to improve security and extend the life of the aging Tangara fleet by up to 12 years. To date, only one of the 55 trains has received the full refurbishment, including a CCTV system.