Drivers in Norwich waiting in their cars could soon receive a knock on the window reminding them to switch off their engines - and a £20 fine if they refuse to do so.

The measure has been introduced by Norwich City Council in a bid to crackdown on air pollution, and could affect drivers waiting to pick children up from school, or for passengers to arrive.

Norwich has had high levels of air pollution for some time - in 2012, a Norwich Air Quality Management Area (AQMA) was set up to monitor levels, and in May Norwich was found to be one of 32 cities around the UK exceeding World Health Organisation (WHO) pollution guidance.

Castle Meadow, St Augustines Street and St Stephens Street are known to be problem areas, and there are hopes ongoing road changes - including the Broadland Northway opening and making parts of the city centre bus-only - will help.

The majority of pollution comes from traffic fumes, not helped by what is known as stationary idling - leaving an engine on while waiting in a vehicle.

Earlier this year, Norwich City Council was granted enforcement powers to fine drivers who leave engines idling £20 under government regulations.

And from this week, council enforcement officers will be approaching drivers - of all vehicles on public roads - found idling to ask them to turn off their engines.

MORE: What can be done to clean up Norwich's air pollution?

Norwich Evening News: Castle Meadow in Norwich. Picture: ANTONY KELLYCastle Meadow in Norwich. Picture: ANTONY KELLY (Image: Archant Norfolk 2018)

And if a driver doesn't comply, they could face a fine of £20.

Vehicles which are moving slowly due to roadworks or congestion, stopped at traffic lights, under test or repair or waiting for a windscreen to defrost will not be included.

Enforcement action will be focused where nitrogen dioxide (NO2) levels are highest, including Castle Meadow and St Stephens Street.

Mike Stonard, city council cabinet member for sustainable and inclusive growth, said: 'The issue of air pollution can present a real danger to health, so there's no doubt it's one we need to address. We know, of course, there is no one solution, but we need to tackle it from a range of angles.

'Major investment in more sustainable transport and infrastructure, so people have a full range of travel options is one priority we have made huge strides in but there are also smaller actions we can take in our day-to-day life that, together, add up to making a meaningful impact.'

He said their focus was not intended to be about penalising drivers, and that there would not be an automatic fine-issuing approach.

'Rather, we are confident that by raising awareness of the issue and how the simple act of switching off an engine can make a real difference, the very vast majority of drivers will comply,' he said.

In December last year, a University of East Anglia study at Riverside Road found the level of drivers who switched off their engines rose from 10pc to 17pc when signs advising them to do so were put up.

The new approach comes just after the council released its 2018 Air Quality Annual Status Report, which paints a picture of air pollution in the AQMA.

There are 29 monitors - made up of two fixed and 27 diffusion tubes - around the city, which monitor levels of NO2 and fine sooty particles, smaller than 2.5 microns, known as PM2.5.

They have been linked to heart and lung disease, cancer and early death.

Norwich Evening News: Denise Carlo. Photo: Dan GrimmerDenise Carlo. Photo: Dan Grimmer (Image: Archant)

Areas of concern - ones which exceed the European Union's limit of 40 micrograms per cubic metre of air (?g/m3) as an annual mean for NO2 - include St Stephens Street, St Augustines Street, Castle Meadow and Riverside Road.

The highest mean NO2 recording last year was on St Augustines Street, at 53.6, an increase in 2013's 51.2.

Of the 29 monitors, seven recorded average readings above 40.

Norwich Evening News: Mike Stonard, a Norwich city councillor. Photo: Steve AdamsMike Stonard, a Norwich city councillor. Photo: Steve Adams (Image: Copyright Archant Norfolk 2016)

MORE: Government issues health warning as air pollution reaches highest grade in Norwich

But there has been improvement - on Chapel Field North, the reading fell from 45.8 in 2016 to 37.1 last year, and at Riverside Road the figure has continually dropped since 2013, despite remaining above 40.

The report says: 'Hence there are still challenges to reduce pollution levels in Norwich but, taken as a whole, the levels are promising as they are still on a slow downward trend.'

But there has been less improvement for PM.25 figures - which is caused by both traffic fumes and wood burning stoves - with a level of 15 recorded at Castle Meadow, the highest figure since 2011 and above the WHO's advised limit of 10.

Denise Carlo, a Green party city councillor, said levels needed to be reduced as a 'matter of urgency'.

She said: 'It is extremely alarming that levels of both particulates and nitrogen dioxide increased at key sites in the city in 2017. Both are extremely dangerous to health, particularly for the young and elderly.

'Traffic pollution produces both these pollutants, and the council must radically reduce traffic, not just in the city centre but across the whole city area. This means fast tracking much better public transport which Norwich has long needed. For particulates, the council also needs to tackle the use of wood burning stoves across the city.'

The city council said, through work with the county council, there had been significant investment in its Transport for Norwich programme, which focuses on sustainable transport.

They used work to remove traffic from St Stephens Street as an example, saying it resulted in a reduction from almost 4,000 vehicles every 12 hours on Rampant Horse Street to just over 1,000.

What measures will the council use to improve air pollution?

The report outlines future work to cut air pollution - both in the community and by the council. It includes:

• Encourage drivers to share journeys via Liftshare, or to use the Norfolk Car Club.

• Take to two wheels - in 2016, there were 43pc more cyclists crossing the inner and outer ring roads than in 2013.

• Encourage schools to develop travel plans using Modeshift Stars software, which supports cycling and walking.

• Signs could be put up reminding drivers to turn off idling engines.

• 'At a later date, it is also intended to look at the option of displaying waiting times at traffic lights and install signage to inform drivers of the AQMA in known congested areas,' the report says.

• Norfolk County Council is looking into monitoring air quality at bus stops with electronic displays.

• Ongoing work to see bus companies replace vehicles with more eco-friendly options.

• A 'long term goal' of the 'removal of private vehicle traffic from Tombland'.

A £1.7m package of work to promote cycling in Earlham Road.

Work to speed up electric car charging points

Work could soon begin to speed up electric car charging points around the city.

The council said there are 25 charging points in the Norwich City Council district boundary, six of which are owned by the council and at Rose Lane car park.

The report says, over the next year, the council aims to upgrade the points to rapid charging, with priority being given to the University of East Anglia's chargers.

And it says, in some larger developments, they hope to make the inclusion of charging points a requirement for house builders.

A lack of charging points nationally has been an issue for drivers hoping to switch to a hybrid or electric model.

Meanwhile, cash incentives offered to promote cleaner cars since 2011 will also be cut from November, along with grants for plug-in hybrid cars, a move which has been criticised by motoring groups.