How Fast Can You Drive With A Roof Box?

How fast you can drive with a roof box depends on several things: the legal speed limit, the guidance supplied for your particular roof box and roof bars, your vehicle, the load you're carrying and the driving conditions.

There isn't a special UK speed limit that applies to a car simply because a roof box has been fitted. However, that doesn't mean you should automatically drive at the maximum legal speed whenever the road allows it. You also need to follow the instructions and limitations applying to the equipment you're using and adjust your speed for wind, rain, traffic and the way the loaded vehicle behaves.

If you're hiring from Midlands Roof Box Hire, we'll professionally fit the equipment before your journey and explain its operation. Here's what you should consider once you get behind the wheel.

Does a Roof Box Have Its Own Speed Limit?

In the UK, fitting a roof box to an ordinary car doesn't by itself create a separate statutory speed limit for that car.

You must still obey the speed limit applying to your vehicle and the road you're using. At the same time, you should check and follow any maximum-speed recommendations or restrictions specified by the manufacturers of the roof box, roof bars and associated equipment.

If an equipment manufacturer specifies a lower maximum speed than the legal road limit, the road being legally suitable for a higher speed isn't a reason to ignore that equipment guidance.

Why Does Speed Matter More With a Roof Box?

A roof box changes the shape of your vehicle. Instead of air flowing only around the original bodywork, you've added a substantial object above the roof.

As speed increases, aerodynamic forces become increasingly significant. This can affect:

• Fuel consumption or electric-vehicle range.
• Wind noise.
• The effect of crosswinds.
• The forces acting on the box and its mounting system.
• The overall feel of the vehicle.

This is one reason a relaxed driving style makes sense when travelling with roof-mounted equipment, even when you're comfortably below the legal speed limit.

Can You Drive at 70mph With a Roof Box?

On a UK road where 70mph is the applicable legal limit for your vehicle, whether that speed is appropriate with your particular roof box setup also depends on the equipment manufacturer's instructions and the conditions at the time.

Don't treat 70mph as a target. It is a maximum legal limit in relevant circumstances, not an instruction to maintain that speed regardless of weather, traffic, load or equipment guidance.

Strong winds, heavy rain, poor visibility or other adverse conditions may make a considerably lower speed appropriate.

If motorway travel is the main reason you're researching this, Can You Drive on the Motorway With a Roof Box? covers the wider motorway considerations in more detail.

What About Thule Roof Boxes?

We use premium Thule roof boxes, but you should always follow the current instructions applicable to the particular box, roof bars and mounting equipment being used.

Don't assume that guidance you've seen for another model automatically applies to yours. If you're hiring from us, we'll supply and professionally install an appropriate setup for your vehicle.

You can find out more about installation at Does roof box hire include fitting?.

Slow Down in Strong Crosswinds

Wind is one of the most important reasons to adapt your speed.

A roof box increases the surface area above the vehicle, so strong crosswinds can be more noticeable than they are during your normal driving. Exposed roads, bridges and open motorway sections deserve particular attention.

Weather can also change substantially during a long journey. Conditions when you left Tamworth might be very different several hours later, so don't base the entire journey on what the car felt like during the first few miles.

If conditions deteriorate, reduce your speed appropriately and follow any weather warnings or road restrictions.

Be Conscious of Large Vehicles

Passing or being passed by a large lorry can temporarily alter the airflow around your car. With additional equipment on the roof, you may be more conscious of these changes.

Keep good control of the vehicle, maintain appropriate spacing and avoid abrupt steering movements. If the car feels unsettled, reducing your speed safely can help you respond to the conditions rather than trying to maintain an unnecessary pace.

Does the Weight Inside the Roof Box Affect How Fast I Should Drive?

Loading matters because the roof box isn't travelling in isolation. You're driving a complete vehicle carrying the box, bars, passengers and luggage.

Stay within the maximum permitted limits applying to the vehicle, roof bars and roof box. Suitable contents should also be distributed appropriately and secured so they cannot freely move as you accelerate, brake or corner.

Remember that litres measure space rather than weight. Our Extra Large 580-litre box may still have empty room when you've reached the applicable load limit.

How Much Weight Can A Roof Box Hold? explains how the different limits interact, while How Do You Pack a Roof Box Properly? covers luggage distribution and securing your belongings.

Does Driving Faster Use More Fuel With a Roof Box?

Speed can have a noticeable effect on aerodynamic drag, so higher-speed driving can make the efficiency penalty associated with roof-mounted equipment more significant.

The precise difference cannot be predicted from the roof box alone. Your car, speed, box, luggage, weather, route, tyres and driving style can all influence fuel consumption.

Electric vehicles face the same aerodynamic issue, although you'll notice the effect in energy consumption and potentially reduced driving range rather than litres of fuel.

See Do Roof Boxes Reduce Fuel Economy? for our dedicated guide to efficiency.

What If the Roof Box Makes More Noise as You Speed Up?

Some change in wind noise can occur after fitting roof-mounted equipment, and it may become more apparent as road speed increases.

However, you shouldn't ignore a sudden new noise that sounds like movement, rattling or something becoming loose.

If you're concerned, find somewhere safe to stop and inspect the setup rather than trying to investigate while driving. Check that the box remains properly closed and locked and follow the instructions supplied for checking the mounting system.

If you've hired the equipment from us and something doesn't seem right, contact us for advice.

Should You Drive More Slowly in the Rain?

Your speed should always reflect the road and weather conditions, roof box or no roof box.

Heavy rain can reduce visibility and grip, increase stopping distances and make standing water more difficult to deal with. Combine poor weather with a fully loaded holiday car and there is even more reason to leave adequate space and avoid unnecessary speed.

The speed limit remains a maximum rather than a recommended speed for every set of conditions.

What About Driving With a Roof Box in Winter?

Cold weather can bring additional complications including ice, snow, strong winds and reduced visibility.

Adapt your driving to the conditions and follow relevant official travel advice. A roof box shouldn't encourage you to maintain your normal dry-weather speed simply because the road has the same posted limit.

If you're using the additional space for winter luggage, remember that bulky doesn't necessarily mean heavy. Check the applicable load limits rather than filling the box solely according to the space available.

Can You Drive Fast With an Empty Roof Box?

An empty roof box may weigh less than a loaded one, but it still changes the vehicle's aerodynamics and remains subject to the instructions applying to the equipment.

Don't assume that an empty box means manufacturer guidance no longer matters.

It also still increases the height of your car. How Much Height Does A Roof Box Add To A Car? is worth reading if your journey involves multi-storey car parks, hotel parking, garages or other height restrictions.

How Fast Can You Drive With a Roof Box in Europe?

Don't assume the rules applying on British roads remain the same after crossing the Channel.

Speed limits and other motoring requirements vary between countries and can also depend on the type of road, vehicle and conditions. Check current official information for every country on your route before travelling.

Equipment guidance continues to matter as well. If a lower maximum applies to your particular roof box or mounting system, entering a country with a higher road speed limit doesn't make that equipment limitation disappear.

For longer trips, Can You Take A Roof Box To Europe? covers insurance, vehicle dimensions, packing and other preparations. If you're travelling by sea, see Can You Take A Roof Box On A Ferry?.

Check the Box Before a High-Speed Journey

Before setting off on a motorway or other high-speed road, take a few minutes to check the complete setup:

• Make sure the roof box is correctly closed and locked.
• Check that the fitted equipment appears secure.
• Make sure the contents are appropriately packed and restrained.
• Stay within all relevant load limits.
• Remove the key from the roof box lock.
• Check the instructions applicable to the box and roof bars.
• Be aware of weather conditions, particularly strong winds.
• Know the approximate overall height of your vehicle.

During a long journey, use suitable stops to carry out further checks in accordance with the guidance for your equipment.

Does Roof Box Size Change the Answer?

You shouldn't determine a safe or appropriate speed simply from whether you're carrying a large or extra-large box.

Our Large option provides around 470 litres of capacity and our Extra Large option around 580 litres, but the correct approach in either case is to follow the instructions applying to the actual equipment and adjust your driving to the vehicle, load and conditions.

If you're still deciding which box suits your trip, Which Is The Best Roof Box? and How Much Can You Put in a Roof Box? can help with the choice.

Roof Box Hire for Long-Distance Journeys

Midlands Roof Box Hire provides professionally fitted roof storage for customers preparing for motorway journeys, family holidays and European road trips. We regularly help motorists from Hinckley, Birmingham, Redditch, Lichfield and Solihull, with our main base in Tamworth.

We can supply a suitable roof box and compatible Roof Bar Hire where required, giving you additional luggage capacity without needing to purchase and store the equipment permanently.

There Isn't One Speed for Every Roof Box Journey

The answer to “how fast can you drive with a roof box?” isn't simply a number. You need to remain within the legal limit, follow the guidance and limitations applying to your particular equipment and choose a speed appropriate for your vehicle, load, road and weather conditions.

Driving a little more steadily can also reduce aerodynamic drag and make a long journey more comfortable, particularly in poor weather or strong winds.

Browse our Roof Box Range, see how much it costs to hire a roof box or Contact Us with your vehicle registration and travel dates to arrange your hire.