Image copyright Getty Images

The Workplace Parking Levy (WPL) could see motorists who drive to work having to pay hundreds of pounds a year for a parking space.

The new charge is part of the Transport Bill, which is expected to be passed by the Scottish Parliament on Thursday.

Environmental groups believe the initiative will help reduce congestion and air pollution by encouraging motorists to walk, cycle or take public transport to work, as well as raising money for local services.

But opponents say it will simply hit businesses and workers in the pocket - and are sceptical about whether people really will choose to ditch their cars.

What are the proposals anyway?

Image copyright PA Image caption The Scottish government says NHS workers would be exempt from the tax

As part of its budget agreement with the Greens, the minority SNP government pledged to allow councils to introduce a WPL if they want to do so.

It would not be a national scheme and local authorities would be free to decide whether to introduce a levy and how to manage it.

If they did introduce it, it would see employers pay an annual levy to the council for every parking space they provide for employees.

Employers could then choose whether to pass on the cost to their staff.

How will it work?

Image copyright Getty Images Image caption The Nottingham scheme has raised more than £50m for sustainable transport projects since 2012

Calls for a tax on workplace parking in Scotland have largely been inspired by a scheme that was introduced in Nottingham in 2012 as part of efforts to reduce traffic congestion in the city.

It had been estimated that commuters driving to and from work accounted for about 70% of peak time traffic in Nottingham.

The Nottingham model sees employers who provide more than 10 parking spaces for their staff pay about £415 every year to the city council for each space, with the charge increasing each year in line with inflation.

Some employers choose to foot the bill themselves but BBC Transport Correspondent Tom Edwards said eight out of 10 workers had the cost passed on to them.

The tax has raised about £9m a year since it started, with the money required by law to be spent on sustainable transport projects.

Staff parking at hospitals and other NHS premises is exempt from the charge, as are disabled parking spaces and front line emergency services such as the ambulance, police and fire services.

The Scottish government has already stressed that NHS workers will not have to pay the levy.

The Nottingham charge also does not apply to parking spaces for motorbikes, customer vehicles, fleet vehicles that are parked at an employer's premise but are not used to travel to and from work, or vehicles that are used to deliver and collect goods.

How many people might have to pay it?

The Scottish Parliament Information Centre (SPICE) used the Nottingham example for a "tentative estimate" of how many people would pay the charge if the City of Edinburgh Council were to introduce a similar scheme.

Its briefing said Nottingham's WPL applied to about 25,000 workplace parking spaces, from a total of 42,000.

It calculated Edinburgh could have about 39,000 workplace parking places liable for the WPL.

The briefing pointed out that more than 330,000 people work in the city and the majority would be completed unaffected by the charge.

What are the benefits?

Image copyright Getty Images Image caption The aim is to cut congestion while raising money for local services

Supporters of a workplace parking tax say it has helped to reduce congestion in Nottingham alongside the improvements to public transport that the scheme has helped to pay for.

It has been predicted that the improvements will take the equivalent of 2.5 million car journeys off the city's roads each year, cutting pollution and carbon emissions as well as reducing travel times for people who do still use their cars.

Public transport is said to now account for more than 40% of journeys in Nottingham, with the city also reported to be the only one in England to have seen a reduction in road journey times during rush hour.

The Nottingham tax is enforceable by law but is said to have had 100% compliance from local employers since it was introduced - and to be very cheap and easy to manage.

Alex Quayle, of Sustainable Transport Scotland, said the Nottingham scheme had clearly been very successful in encouraging people to change their commuting habits.

But not everyone is happy?

Image copyright Getty Images Image caption Opponents of the tax say many parents with school-age children would struggle to get to work on time without a car

Critics argue that many people - for example parents who drop their kids off at school as part of their morning commute - are simply unable to get public transport to work, far less walk or cycle.

Motoring journalist Alan Douglas argued that it was therefore "nonsense" to suggest that people would change their habits, and that the vast majority would just "bite the bullet and pay".

He added: "What we need to get people out of their cars - if we want to get people out of their cars - is to provide better public transport.

"The fact is people use their cars because the public transport is not there, and we have seen from the problems with ScotRail that people would want to use it but they can't depend on it so they use their cars as the best alternative."