Why passengers are being barred from rear carriages on these Sydney trains

People have been spotted riding on the back of Tangara trains, prompting a crackdown. ( Supplied: NSW Government )

Frequent incidents of train surfing and vandalism have prompted a security crackdown on Tangara trains, with rear carriages to be shut throughout the NSW school holiday period.

The lack of CCTV on the trains has made them susceptible to vandalism, as has the "buffer": a platform at the rear from which train surfers can jump from the platform.

Only one out of 55 Tangara trains has been refurbished two years on from a state government pledge to upgrade the aging fleet and install CCTV.

Passengers are being barred from using the rear carriages of all Tangara trains to prevent people breaking into the crew cabs and riding on the back of them.

The policy was already in force on selected night-time and weekend services, but has now been applied to every Tangara train for the duration of the school holidays.

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 out of 55 Tangara trains has received the full refurbishment, including a CCTV system.

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