By Geoff Adams-Spink
BBC News website disability affairs reporter
Disability organisations have criticised the government's decision to give rail companies another 16 years to ensure that trains are fully accessible.
The announcement of the 2020 end date was made just three days after the Disability Discrimination Bill - which will improve the rights of disabled people - was published in the House of Lords.
Disabled travellers will have to wait another 16 years for full access
"Trains are a vital link in the accessible transport chain," said transport minister Charlotte Atkins.
"It is important that disabled people have confidence that, when travelling by rail, the train that arrives will be accessible to them."
Leonard Cheshire - a disability charity which has been campaigning on transport accessibility - says 2020 is "later than we would have liked".
"The key now is to ensure that these regulations are properly enforced," said the organisation's head of policy, John Knight.
Mr Knight thinks that although it is a relief to have an end date that train operators have to work towards, the important thing is make sure that the regulations are watertight.
"Some elements in the rail industry have already hinted that they could ignore the regulations," he said.
"They must be told that disabled people and the government won't let this happen.
"Sixteen years is long enough to wait."
A parliamentary committee, which had examined a draft of the Disability Discrimination Bill before it was published, had recommended a deadline of 2017 for rail accessibility.
Another disability organisation, RADAR, says putting the date back by another three years is "disappointing".
"An accessible and integrated transport system is vital if disabled people are to be allowed to achieve full social inclusion," said RADAR chief executive, Kate Nash.
She says an extra three years will mean more frustration and isolation for disabled travellers.
Kate Nash says rail access is needed for full inclusion
"Train companies have had ample time to make these adjustments," she said.
The Disability Rights Commission, the body which oversees the rights of disabled people in the UK, describes 2020 as "a clear point on the horizon" which disabled people can look forward to.
"Whether the deadline was 2017, as we hoped, or 2020 as the government has now pledged, train companies will need to begin work now to meet this important date," a spokesperson said.
New trains have had to comply with accessibility regulations governing audio and visual information systems, wheelchair accommodation and accessible toilets since 1999.
Existing rolling-stock will be upgraded as and when it is refurbished.
The government says there are almost 2,000 accessible train carriages in service, with another 700 expected in the next 18 months.