How will the petrol and diesel ban work?
All new cars in the UK will be "effectively zero emission" by 2040, under plans to tackle air pollution.
The government is under pressure to bring forward this deadline and ban all sales of new petrol and diesel cars by 2032, after a report by a parliamentary committee described its plans as "vague and unambitious".
But with electric cars currently accounting for less than 1% of new sales, the switch will mean seismic changes, and gives rise to a host of pressing questions.
Why are petrol and diesel cars being banned?
Poor air quality is the "biggest environmental risk to public health in the UK" - thought to be linked to about 40,000 premature deaths a year - the government says. While air pollution has been mostly falling, in many cities nitrogen oxides - which form part of the discharge from car exhausts - regularly breach safe levels .
Diesel vehicles produce the overwhelming majority of nitrogen oxide gases coming from roadside sources.
The government was ordered by the courts to produce a new plan to tackle illegal levels of harmful pollutant nitrogen dioxide, a form of the nitrogen oxide pollutants emitted by vehicles.
Hybrid vehicles, which combine petrol and electric motors, will not be included in the sales ban.
Concern about air pollution is not new, but the issue has risen to prominence because the UK government lost court cases over its plans to reduce nitrogen dioxide levels. It has been compounded by the fact car makers were found to be cheating emissions tests.
It also comes amid growing concerns about the impact of global warming.
A report by the UN's Intergovernmental Panel on Climate Change has warned that "rapid, far-reaching and unprecedented changes in all aspects of society" are needed to keep global temperatures from rising by more than 1.5C.
Among its recommendations, the report urges people to switch to electric vehicles to reduce carbon emissions.
What else is being done to reduce pollution?
As well as the future ban on petrol and diesel cars, more than £200m is being given to local authorities to draw up plans to tackle particular roads with high pollution. This is all part of the same package of measures from the government.
Will tax revenues from petrol and diesel dry up?
It's likely the government will have to change the way fuel is taxed to make up for losing billions of pounds at the pump.
The government raised about £27.9bn from fuel duties in 2016-17, according to the Office for Budget Responsibility. That's getting on for 4% of the total tax take.
Say I buy an electric car... where will I recharge it?
There are more than 6,500 locations with charging points around the UK, according to website Zap-Map.com and new locations are being added daily.
But if mass market ownership of electric cars is to be viable, there will need to be on-demand access to power points. This raises a number of potential problems. For example, where will power points be sited? Will roads have to be dug up for cabling? Will drivers have to share power points, and so be restricted to certain charging times?
For people who live in a flat or don't have off-street parking, electric vehicles may not be practical if there is not a public charging point nearby.
One option is to ask the local authority to install a charge point in the relevant street. The government has set aside £4.5m to fund such applications over the next two years and will cover up to 75% of installation costs.
It also offers subsidies to employers who install charging points at workplaces.
However, it can take up to eight hours to charge an electric vehicle, so more efficient batteries will be needed.
While some vehicles can only travel up to 50 miles between charges, others can manage more than 200 miles. This puts commuting and city driving within reach, but makes long distance journeys more of a challenge.
What would happen if I ran out of charge mid-drive?
It doesn't happen a lot, said Tom Callow, of Chargemaster, the UK's largest provider of electric vehicle charging infrastructure. Cars alert drivers in plenty of time.
Electric cars give drivers a range or countdown. On long journeys, drivers need to plan ahead. Navigation systems in electric cars can factor in charging points on the way to a destination as they plot a route for the driver.
"The reality is that once you start driving an electric car it is a different kind of culture," said Mr Callow. "You are not filling up, you are topping up and you drive differently and top up when available."
Will the National Grid be able to cope? The electricity demands will be massive.
The National Grid says electric vehicles could drive large increases in peak power demand, but it will be able to cope. This is despite concerns the grid is already strained at times by the demands of charging electric vehicles.
A 2017 report by the think tank Green Alliance warned that as few as six vehicles charging at the same time, close to each other, could cause localised power drops.
Smart charging, which intelligently controls when vehicles draw electricity from the grid to avoid peaks and troughs, is one way of managing the situation. It is a developing technology and there is even speculation car batteries could return power to the grid to help smooth out demand.
But if the additional demand from vehicles is not managed carefully, it will "create challenges across all sections of the energy system, particularly at peak times", according to forecasts in the grid's Future Energy Scenarios report, released earlier this year.
However, not all vehicle owners will switch to electric replacements when their petrol or diesel ones finally stop running. For example, it is expected that some of the owners of heavy goods and public service vehicles may switch them to natural gas or hydrogen powered modules rather than electric.
What about paying for old cars to be scrapped?
According to its consultation, the government believed a so-called scrappage scheme would take 15,000 of the most polluting diesel and petrol cars off the road in a year.
Drivers would be given about £8,000 to switch to a fully electric alternative, meaning the government would have to fork out £110m. The impact on emissions of nitrogen dioxide would be to cut them by 0.02%, not a huge change in the grand scheme of things.
The Treasury is believed to have objected strongly because of the cost, but also on the grounds it would be hard to target the scheme at those who most need it - and prevent it becoming a subsidy for drivers who could already afford to change to electric vehicles.
Why not ban the dirtiest vehicles from the most polluted roads?
Environmental campaigners believe creating what are termed "clean air zones" (CAZs) in the most polluted towns and cities is the most effective and speedy way of reducing emissions of nitrogen dioxide. Councils will be able to impose these zones and will be able to block certain vehicles or impose a daily charge on drivers.
But the government hopes they won't do this. While its own research suggests CAZs are the most effective means of getting emissions down, cutting them by 18% compared with 0.02% for a scrappage scheme, policy makers argue they are too blunt an instrument and can cause all sorts of complications for local areas. For example, if a council in one town imposes a clean air zone and its neighbour doesn't, will traffic (and the emissions they cause) merely move to the cheaper location?
Most of the breaches with diesel emissions happen on 81 roads around the UK, says the government, in vast swathes in the hearts of urban areas. It wants councils to target these roads with a range of tactics that cut nitrogen dioxide, including removing speed bumps and changing traffic lights so that traffic isn't slowing or speeding.
However, recognising that this might not be enough, the plan does give local authorities the power to charge or ban drivers on certain sections of road.
How do diesel and petrol compare as pollutants?
Sales of diesel cars surged in the early 2000s as drivers were encouraged to choose them because they had lower climate-warming carbon dioxide emissions than petrol cars.
While diesel cars are the biggest single source of nitrogen oxide emissions, diesel powered buses, coaches and - especially - heavy goods vehicles are the really heavy polluters, producing eight to 10 times the amount of gases per kilometre than cars. There are, however, many more cars.
Does this mean London's congestion charge will spread to other cities?
The government isn't keen. Establishing a clean air zone (CAZ) for which motorists would be charged to drive into could simply move the pollution problem elsewhere rather than solve it. Policy makers believe that by targeting the 81 roads around the UK that are the main cause of the problem, they can prevent the type of emissions transfer that could happen if one town has a big CAZ and its neighbour did not.
What about those who need a larger car in the class of a Ford Galaxy, or one to tow a caravan?
Tom Callow, of Chargemaster, told the BBC: "There are a couple of cars available on the market now which are capable of towing trailers. While they are not exactly like a Ford Galaxy they are equivalent to SUVs or estates or saloon cars."
Will motorcyclists be affected?
Potentially, but only those who drive the very oldest bikes. Essentially, motorcycles built before the year 2000 could face fines if councils decide to impose charges or bans on some roads. The government is currently giving a grant of £1,500 for the purchase of an ultra-low emission motorcycle.
What about other vehicles?
The government's 2040 target only applies to cars and vans.
However in its Road to Zero Strategy published earlier this year it said ultimately it wants a transition to zero emissions across all vehicle types.
The government said it was working with industry to develop an ultra low emission standard for trucks and is introducing a voluntary industry-supported commitment to reduce heavy goods vehicle greenhouse gases by 15% by 2025, from 2015 levels.
It is also working to clean up its bus fleet by investing in new low emission buses and retrofitting emission-reduction technology to existing vehicles.
What about aeroplanes? How much air pollution is caused by aircraft?
In the UK about 1% of nitrogen dioxide emissions are caused by aviation. Far more are caused by people driving to airports in their cars.
What about hydrogen-powered vehicles, as opposed to electric?
The government has already announced a £23m fund to boost the uptake of hydrogen vehicles.
At the time it said hydrogen vehicles could play a "vital role" alongside electric vehicles in cutting harmful emissions.