Gritting the Roads During a Heatwave?
Seeing the council gritting wagons doing their job is a common sight during the winter as they provide an essential service to help keep the roads safe and free of ice. The very same trucks can also sometimes be spotted in the summer, especially during a heatwave. While it may seem strange at first, this is not a mistake or mirage caused by sunstroke. Gritting trucks play a huge role in keeping the roads safe in hot temperatures. They help to combat the very real risk of roads melting by spreading rock salt.
What Causes Roads to Melt?
Around 95% of UK roads are made of tarmac, also known as asphalt. Once tarmac reaches a certain temperature - generally 50°C - it starts to melt. While this may seem like a miracle here in the UK, this refers to the temperature of the tarmac itself - not the outdoor air, which is usually measured in the shade and above ground. This means that as soon as temperatures consistently exceed 30°C, the tarmac can start melting.
Roads in the sun can get as hot as 50°C, and at these temperatures, they begin to become soft.
This process is called binder flushing or bleeding. It happens when asphalt binder (the ‘glue’ that holds tarmac together) rises to the surface of the road, often due to heat. The binder can then expand and become more fluid, causing the road surfaces to become shiny and slippery, increasing the risk of accidents. Melted tarmac can also stick to the cars damaging tyres and paint if not removed properly and cause long-term damage to the road surface, which is notoriously difficult and costly to fix.
Because of this, if you suspect a road is melting, make sure to report it to your local council's highways department. It is also important to drive slowly and carefully, so avoid sudden braking or sharp turns.
While this may seem like a rare phenomenon, in 2022 two roads located in Northern England melted. One of them was a road in Stockport, Greater Manchester.
This wasn’t the first time it had happened either. During a heatwave back in 2019, a major A-road had to be closed due to melting tarmac. Photos taken at the location showed multiple cracks in a new section of the A11 in Norfolk.
However, this issue doesn’t only affect cars. In July 2022, the hot temperatures caused the tarmac on Luton Airport’s runway to melt. This resulted in many delays as the airport had to suspend all flights.
After this event, many gritters were sent out across the UK to help keep the roads safe and minimise the damage caused by the hot weather.
How Does Gritting in the Summer Work?
While gritting is typically associated with icy roads and snow, it also plays a surprising role in protecting our roads in spring and summer. Instead of preventing ice from forming, it helps to stop the roads from melting.
During the hot temperatures, councils across the UK often send out gritters to spread rock salt across the road surface. This helps to form a non-stick, protective barrier between the hot tarmac and the cars, minimising the damage to the roads.
Sometimes, graphite dust will also be spread to further improve the grip for the drivers and lower the chance of accidents. This method has been commonly used by the Lancashire County Council.
We’ve been using around six of our gritting fleet to apply granite dust where this is happening. This creates a barrier to stop it sticking to people’s tyres and improve skid resistance. In some places we are also putting out signs with advisory speed limits to encourage drivers to slow down.
But how does the salt help to stop the roads from melting? It has the ability to attract moisture from the air, helping to cool the tarmac down. It works best if the salt is put down early in the morning or in the evening, before the road gets too hot.
Because of this, just like in winter, the councils keep a close eye on the weather forecast. This allows them to make informed decisions about when to grit the roads. Once decided, the same gritters that are used in winter are usually used for summer gritting too. They follow planned routes made by the council, often prioritising the most important roads.
How Do Other Countries Deal With Hot Temperatures?
The UK is not the only place that uses grit to protect roads during hot weather. Some areas in the Netherlands, especially in the east, near the German border, also use grit in the summer to stop the roads from getting damaged.
In addition to gritting, Japan also takes extra steps to protect roads and help people stay cool. In some places, like Tokyo, they use misting systems. These spray fine water mist to cool the roads and make public spaces more comfortable to be in, especially when it's very hot and humid.
Known for its power to melt ice, rock salt also helps protect roads during hot weather. In heatwaves, it can soak up moisture and help cool the road surface, stopping the tarmac from melting. This clever use of salt is common in other countries too, like the Netherlands and Japan.
