The ban is expected to be introduced in 2023, four years after it was approved by MSPs following more than a decade of lobbying.
Cars and vans parked on pavements can prevent the elderly and disabled, including those in wheelchairs, along with parents with pushchairs, from using them, or force them onto roads.
However, pedestrians’ lobby group Living Streets is worried pavement parking will continue on “vast swathes” of streets because cars being parked on the road instead would prevent ambulances and fire engines from getting past.
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It has spotted the loophole in regulations which have just been issued by the Scottish Government to local authorities, who will be responsible for designating streets for the ban and enforcing it.
Living Streets Scotland director Stuart Hay said: “We have significant concerns about guidance allowing local authorities to allow pavement parking where access for emergency vehicles is deemed an issue.
"Fire engines shouldn’t become a Trojan horse which allows pavement parking to continue on narrow streets.
"The sensible response is to ban parking on one, or both sides of the street, if necessary, to make sure that fire engines can get through.
"As it stands, we fear some local authorities will exempt vast swathes of their streets to duck implementing the ban properly.
“It’s important these regulations are now finalised so the ban, which was passed into law into in 2019, is in place by 2023.
"It’s been a long wait for older, disabled people, children and parents who continue to be denied access to safe pavements in their communities.”
Hay said the exemption was likely to apply in areas such as Portobello in Edinburgh, where access for fire engines was already a problem on several streets.
The potential setback for campaigners comes eight months after Scotland on Sunday revealed the introduction of the ban had been delayed to 2023 by the Covid pandemic.
Transport Secretary Michael Matheson has described pavement parking as a “bane of many people’s lives”.
He said last April that he expected councils would need about a year to assess their streets, “so I would probably say it’s going to be into 2023 before they will be in a position to take forward the necessary enforcement action and designate the streets where pavement parking will not be permitted.”
At the time, the minister said he expected a consultation with local authorities over implementing the ban would start in summer 2021.
However, it was not published until December and will run until March.
A spokesperson for the Scottish Government’s Transport Scotland agency said: “The consultation seeks views on when a local authority should be able to exempt an area of footway from the national pavement parking ban.
"We have set out a proposal whereby a local authority would be able to take into account the fact that emergency access to a street may be blocked if cars were to park on both sides of the carriageway.
"In these circumstances, it may be beneficial to give the local authorities discretion to allow, for example, parking on the pavement on one side of the street to maintain access.”