And it doesn’t take into account whether there are hills on a child’s walk.

Last week the Mercury reported on the case of eight-year old Sienna Schubert, who Transport for NSW declared was not eligible for a free bus pass because she lived 100 metres too close to her school.

Transport for NSW rules state students in Years 3-6 have to live at least a 2.3-kilometre walk from their school to get a free bus pass – which a Transport for NSW spokeswoman described as “one of the most generously subsidised travel schemes in the world”.

Sienna’s house is 2.2 kilometres away, so she misses out.

READ MORE: ‘Give the girl a bus pass, you tossers’ – readers angry

Transport for NSW uses two measurements between a child’s house and school to determine whether they are eligible for a free bus pass – walking distance and ‘as the crow flies’.

“When assessing pass eligibility our systems first measure straight line distance, then if inside the straight line distance, we will measure the required walking distance,” the Transport for NSW spokeswoman said.

“NSW’s School Student Transport Scheme already has some of the shortest walking distance requirements in Australia.”

The spokeswoman said those measurements had not been changed for 22 years.

“The current eligibility guidelines regarding walking distances for primary and secondary school students have been in place since 1996, after a series of reforms recommended by a parliamentary committee,” she said.

“This committee also set the distance criteria for the different school levels.”

The spokeswoman did not state how regularly the walking distances are reviewed and whether Transport for NSW planned to do so in the near future.

“Transport for NSW also partners with industry leaders and peak bodies to review the safe walking guidelines and looks at ways in which the School Student Transport Scheme can continue to meet demand,” she said.

She said the 2.3-kilometre walking distance that comes into force when a student enters Year 3 did not take into account how hilly a child’s walk may be.

“Gradient is not included in the 2.3k-kilometre measure but Transport for NSW does take local road and traffic conditions into account during these reviews,” the spokeswoman said.

There may be “special circumstances” that affect some children’s journey to school, which was why an independent appeals panel was in place for parents “who believe that an eligibility decision should be reviewed for any reason”.