Cars don't just cause climate change – they make our streets hotter today

​As Hackney braces for more frequent heatwaves, most discussions focus on climate change and carbon emissions.

But there's another important reason to reduce traffic in our neighbourhoods: cars and vans make our streets hotter right now.

Motor vehicles don't simply pollute the air and emit carbon dioxide. They also act as thousands of small heaters spread across our streets, adding heat directly into the urban environment and making heatwaves more dangerous.

Traffic is a hidden source of urban heating

Many people have heard of the "urban heat island" effect. This describes how cities become hotter than surrounding countryside because buildings, roads and pavements absorb heat from the sun during the day and slowly release it at night.

But researchers are increasingly recognising that traffic itself is a significant and often overlooked source of heat.
Every petrol or diesel car is essentially an inefficient heat engine. Only a fraction of the fuel's energy is used to move the vehicle. Most of the energy is lost as heat through:
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• Hot exhaust gases
• Engines and radiators
• Tyres and brakes
• Warm vehicle surfaces

​Electric vehicles are more efficient, but they still produce waste heat from motors, batteries, brakes and tyres.

Thousands of vehicles moving through busy urban streets can therefore create a substantial amount of additional warming, particularly in dense areas where heat becomes trapped between buildings.

Recent research from the University of Manchester has developed new methods for measuring traffic-generated heat and found that vehicle use can measurably increase urban temperatures and alter how heat moves between roads, buildings and the surrounding air.

Extreme temperaures in Hackney, not unusual

​​Parked cars also make neighbourhoods hotter

The effect isn't limited to moving traffic.

A study published in 2025 found that parked cars have been largely ignored in urban heat studies, despite covering large areas of our streets. Vehicles parked along kerbs absorb sunlight and store heat, changing the thermal properties of the street and contributing to warmer local temperatures.

On a sunny day anyone touching the bonnet of a parked car already knows this instinctively. Cars become remarkably hot because they absorb and retain solar energy. Multiplied by hundreds or thousands of parked vehicles, this becomes an important factor in how hot our neighbourhoods feel.

Congestion can increase temperatures

Traffic congestion appears to make matters worse.

Research in Chicago found that slower-moving traffic was associated with increases in urban heat island intensity. Put simply, traffic jams do not only waste time and worsen air pollution – they may also make cities hotter.

This matters because heat is not just uncomfortable. It is dangerous.

High temperatures increase the risk of dehydration, heat exhaustion, heatstroke and cardiovascular illness. Older people, children, and those with underlying health conditions are particularly vulnerable.

Warm nights can be especially harmful because our bodies need cooler temperatures to recover from daytime heat.

Hackney main road traffic

​Roads and parking spaces are part of the problem

Cars affect temperatures in another important way: they require large amounts of land.

Roads, car parks and paved surfaces absorb solar radiation very efficiently. Dark asphalt can become much hotter than nearby green spaces during sunny weather.

Trees and soil cool the environment through shade and evaporation. Asphalt does the opposite. It stores heat during the day and releases it slowly overnight, keeping neighbourhoods warmer long after sunset.

This means that reducing traffic can have a double benefit:

• Fewer vehicles producing waste heat
• More opportunities to replace road space and parking with trees, rain gardens and other greenery

We already know how to cool our neighbourhoods

The encouraging news is that many of the solutions are already well understood, and are being introduced to an extent in Hackney.

Research consistently shows that cities can reduce temperatures by:

• Planting more street trees
• Expanding parks and green spaces
• Creating rain gardens and planted verges
• Using lighter-coloured materials that reflect sunlight
• Reducing motor traffic
• Supporting walking, wheeling, cycling and public transport

Cities around the world are beginning to demonstrate what is possible. Medellín in Colombia has reportedly reduced temperatures in some areas by around 2°C through extensive planting programmes and green corridors.

Amhurst Road sustainable drainage planting

Low-traffic neighbourhoods are climate adaptation

Low-traffic neighbourhoods are often discussed in terms of cleaner air, safer streets and reducing carbon emissions. These benefits remain hugely important.

But there is another reason to support them.

As summers become hotter, reducing motor traffic can help make our streets cooler and more comfortable places to live. Fewer cars mean less waste heat, less asphalt dedicated to traffic and parking, and more space for trees and greenery that actively cool neighbourhoods.

Heatwaves are becoming one of the greatest public health challenges facing UK cities.

Creating streets designed for people rather than through-traffic will not solve climate change on its own. But it is one practical step we can take now to make Hackney and other urban areas healthier, greener and more resilient to the hotter summers that are increasingly becoming our new normal.

Conclusion

If we want neighbourhoods that remain liveable during hotter summers, we need fewer heat-generating vehicles and more space devoted to people, trees and nature.