The question whether wheelchair users should have priority on buses over mothers with baby buggies is to be considered by the highest court in the UK.
Proceedings at the Supreme Court follow a decision by Court of Appeal judges that a mother was within her rights when she occupied the reserved space also used by disabled travellers.
The ruling was a defeat for wheelchair user Doug Paulley, from Wetherby, West Yorkshire, but he was later granted permission to continue his legal battle because it raises issues of public importance.
Mr Paulley attempted to board a bus operated by FirstGroup which had a sign saying: ''Please give up this space if needed for a wheelchair user.''
But he was left behind at the stop because a woman with a sleeping baby in a pushchair refused to move out of the designated area when asked by the bus driver, saying the buggy would not fold.
The appeal judges rejected Mr Paulley's claim of unlawful discrimination.
FirstGroup has a policy of ''requesting but not requiring'' non-disabled travellers, including those with babies and pushchairs, to vacate the space if it is needed by a wheelchair user.
A judge at Leeds County Court ruled the policy was discriminatory and in breach of a duty under the Equality Act 2010 to make reasonable adjustments for disabled people.
Mr Paulley won £5,500 in damages against FirstGroup after Recorder Paul Isaacs said the company should have taken measures to ensure he was not at a disadvantage when he tried to get on the bus.
But that decision was overturned by the appeal court judges and the case will now be considered by a panel of seven Supreme Court justices in London.
Mr Paulley said in a statement: "It is not right that I, and other wheelchair users, should be nervously looking to see if anybody is in the wheelchair space and wondering what will happen.
"This can cause a great deal of distress. Wheelchair spaces are the only place on the bus that wheelchair users can travel in; if they aren't available, wheelchair users can't travel. This is the single biggest barrier experienced by wheelchair users when accessing transport, and most wheelchair users experience this.
"Bus companies need to have clear policies so that we can have a culture where non-disabled people automatically move to other areas. More needs to be done to ensure that this space is available to wheelchair users when needed."
Chris Fry, of Unity Law, which represents Mr Paulley, said it was the first case of its kind to be heard by the Supreme Court and added: "We hope that the Supreme Court will finally make the correct legal and moral decision that supports the overriding objective of social inclusion for disabled people, and find in favour of Doug."
David Isaac, chairman of the Equality and Human Rights Commission in the UK, said: "This is not about pushchairs versus wheelchairs but confusing policies from bus companies that cause problems. Bus companies have a duty to allow wheelchair users to travel given how vital this is to disabled people being able to live independent lives."
Justine Roberts, Mumsnet chief executive, said: "The general consensus on Mumsnet is that when it comes to the priority space, wheelchair users take precedence.
"A lack of space on crowded buses can cause problems for those with travelling with pushchairs, shopping and babies; Mumsnet users would like to see more flexible space for storage, but certainly not at the expense of wheelchair users."
Rosemary Frazer, campaigns manager at disability charity Scope, said: "We hope this case will provide clarity for all bus users.
"It's really hard to get around on buses when you have a buggy and young children, but it's even harder when you are disabled.
"Before accessible spaces were brought in, it was impossible for wheelchair users to use the bus - I wasn't able to use a bus until I was 30.
"Companies allocated accessible spaces on buses following a sustained campaign by disabled people. Today they are often a lifeline into work and the community.
"Most people don't realise just how difficult it is for disabled people to get around, to work, the shops, or to visit friends.
"We'd like to see transport companies looking for ways to make it easier for all of their customers to use their services."