Eco zealots are warning that the increasing dimensions of new cars - particularly 'oversized SUVs' - will wipe out one in ten roadside parking spaces in UK cities by 2040.

They say growing vehicle size poses an 'unprecedented threat to urban space' that will 'eliminate vast numbers of parking spaces' over the next decade.

New cars have been 'getting steadily bigger' for decades. They are becoming longer, wider and taller, with higher bonnets each year, according to analysis by green think tank Transport & Environment.

This is despite family sizes and car occupancy declining, 'leaving vehicles taking up more room while carrying fewer people'.

T&E claims that if the trend of 'carspreading' continues, city authorities will be forced to redesign their roads to accommodate bigger motors.

This will cut on-street parking capacity by between 8.5 and 14 per cent by 2040, with London alone set to lose approximately 100,000 spaces, it forecasts.

The report shows this is being driven by a sustained increase in vehicle size since 2000.

Newly sold cars in Britain are - on average - getting longer by 1.2cm each year.

Vehicle height, width and bonnet height are all rising by around 0.5cm annually.

T&E has accused carmakers of 'shifting away' from smaller models in favour of larger, more profitable vehicles, accelerating the squeeze on urban space.

'After 25 years of relentless growth, our streets are dominated by oversized SUVs that cities simply weren't designed for,' explained Anna Krajinska, T&E UK director.

'The result is a lose-lose: councils are forced to reshape streets around larger vehicles, sacrificing parking capacity, public space and safety in the process.

'This is a market failure. Without clear standards to limit car size and encourage right-sizing, carspreading will continue unchecked, and cities will keep paying the price.'

A recent study found that the average width of a new car is increasing by 1cm every two years.

The report, published in 2024 and analysing every new model on sale in Britain, found that the average width of a car in showrooms was 180.3cm in the first half of 2023.

Five years earlier, the average was just 177.8cm in 2018.

Historical data held by the International Council on Clean Transportation (ICCT) shows that this trend - of new cars increasing in width by 1cm every two years - had been ongoing for the two decades up to 2020.

The report pinpointed certain cars as having grown substantially, with the new-generation Land Rover Defender 20cm wider than the old 4X4, and BMW's X5 growing 6cm in six years.

Why are cars getting bigger? 

Motor manufacturers have not refuted claims that cars are getting larger, saying it is a consequence of stricter crash protection regulations.

The requirement for crumple zones, increased structural integrity, more airbags and additional safety technology has ultimately impacted the average car's dimensions.

Manufacturers must incorporate these to comply with increasingly stringent regulations, with all passenger car proportions - not just SUVs - expanding to accommodate them.

Though this is certainly for the greater good, as crash data shows.

Over the last 20 years, Department for Transport data shows that the number of car occupant casualties has dropped from 183,858 in 2004 to just 70,089 in 2024.

In fact, car occupants accounted for just over half (54 per cent) of road collision casualties last year, down from two-thirds 20 years ago.

But the popularity of SUVs has grown dramatically over that period.

A decade ago, around one in ten new cars entering UK roads were SUV models. But in 2024, they became the most popular body style, overtaking supermini with a 33 per cent market share that continues to increase.

Analysis by CarGurus last year found that more than half (52 per cent) of new cars in showrooms are now SUVs. 

Bigger SUVs will 'lead to 400 additional road deaths in UK and Europe by 2040'

T&E - along with fellow green think tank Clean Cities - says the rise of ever-larger SUVs could lead to around 400 additional road deaths annually by 2040 across the UK and Europe, compared with a 'right-sizing' scenario, where smaller models are prioritised for the market.

It projects a growing gap in deaths among vulnerable road users - pedestrians, cyclists, motorcyclists and moped users.

Under the current trajectory of increasing vehicle sizes, the two groups claim that 40 per cent more children walking could be killed in car crashes by 2040 compared with vehicle right-sizing.

'Rising bonnet heights, which are projected to reach a fleet average of 86.2cm by 2040, pose a particular risk to children,' the campaigners state.

'While adult pedestrians would most likely be hit in the vital organs or torso in crashes, children run a higher risk of being struck in the head or chest.'

Oliver Lord, director of Clean Cities, said carspreading is 'fast becoming a public health crisis'.

He told us: 'How many more reports are needed, or kids killed, before the car industry stops peddling massive and unnecessary SUVs?

'The relentless increase in the size of cars is not just stealing public space but also making our streets more dangerous. There's no way city leaders can continue to turn a blind eye to this problem - whether traffic congestion, parking stress or road deaths - they must act now.'

To combat the threats to urban space and safety, T&E UK and Clean Cities call for immediate policy changes to shift the UK car market towards safer, more efficient and compact models, including a 'large vehicle levy': a tax on the sale price of SUVs and larger motor vehicles.

They too want an industry-wide cap on dimensions. Bonnets should be no higher than 85cm, and a car's width limited to no more than 192cm.

These dimension restrictions should come into force for newly type-approved models from 2033 and apply to every new car on sale by 2036.

The groups also want Euro NCAP to incorporate visibility testing, especially how close to the bonnet drivers can see small children in front of them.

And they are calling for the UK to impose higher parking charges for larger and heavier models.