The new train rules have come into effect for the rest of the day, with the exception of a few hours of peak-hour service on Saturdays and Sundays.
Passengers who arrive at stations at 7.15am, 7.25am, 8am, 9am and 11am are free to drive their car to their destination.
A passenger with a valid permit to drive can drive to their home station and the car can be checked for safety, but not on the train.
In total, passenger and vehicle safety have been improved by 1.6 per cent on the day.
There are currently 3.9 million passenger journeys taking place in the Sydney metropolitan area, which is the third largest in Australia after Melbourne and Brisbane.