What Happens if Road Surfaces Become Soft in Hot Weather?
You might get this question as part of your driving theory test:
What will be affected if the road surface becomes soft in hot weather?
The exhaust
The suspension
Tyre grip
Fuel consumption
The answer they’re looking for is C: If the road surface becomes soft in hot weather, it can affect your tyre grip. And because it will affect your tyre grip, it will also affect your braking.
The Effect of Hot Weather on Road Surfaces
High temperatures can cause tarmac to melt. In the UK, certain roads have melted on particularly hot summer days with highs of 35.5°C. This might be a high temperature for the UK, but is that really hot enough to cause a solid road surface to melt?
The issue is that we usually measure temperature in the shade, and road surfaces can get significantly hotter than anywhere else. This is because:
Dark road surfaces can absorb heat.
Friction from car tyres, and heat from car exhausts, can increase the ground temperature even further.
Because of this, on especially hot days, the temperature of roads can get as high as 50°C. At this temperature, the road surface can start to soften.
Do All Roads Get Soft on Hot Days?
The likelihood of a road softening in hot weather will depend on a number of factors:
The road’s exposure to direct sunlight and wind.
Whether the road surface is light, or dark.
The amount of traffic using the road.
The road’s material can also make a difference. Certain high traffic roads on the UK are paved with an asphalt containing polymer modified binders, which can raise the softening point of the road to approximately 80°C. But many roads in the UK are paved with a combination of asphalt and concrete, which is considerably less durable.
Adapting Your Driving to the Weather
There are many driving theory questions that relate to the weather, but they usually ask you to consider the risks of driving in cold, wet, or windy conditions. However, it’s also important to be aware of the risks of driving in hot weather, and the precautions you should take.
How to Drive in Hot Weather
Soft road surfaces can increase your braking speed. Beyond this, consider the following:
Read our full guide to staying safe while driving in a heatwave.
Make Sure You Have All The Cover You Need
Because high temperatures can affect your car’s battery, breakdowns may also be more likely when it’s hot.
When driving in the warmer seasons, make sure you keep a bottle of water in the car so you can stay hydrated if you breakdown. Also, consider adding breakdown cover to your comprehensive car insurance policy.
