Banner of horsebox on weighing scales


Horsebox Safety Week: Watch your weight

Don't pile on the pounds

Just as obesity in horses and ponies poses a threat to their welfare, so does overloading the horsebox or trailer in which they have to travel. Few horse owners would ask their mount to carry more weight than it could bear and yet, as an independent equine transport specialist and former DVSA examiner, I have seen countless horseboxes and trailers overloaded to the point that the vehicle was both illegal and represented a real threat to the welfare of the animals inside.

Remember the game of Buckaroo where each player carefully loads an item onto the mule and waits to see which item will tip the delicate balance and cause the mule to buck? Overloading a horsebox or trailer is much the same and puts mechanical strain on the vehicle, makes it harder to stop and, like the mule in Buckaroo, makes everything less stable and predictable.

What many people fail to realise is that they are putting themselves and their animals at risk by overloading the horsebox or trailer in which they are travelling: but how do you make sure that you are not overloading your horsebox or trailer?

To work out how much you can carry in your horsebox or trailer, you will also need to know the Maximum Authorised Mass (MAM), often referred to as The Gross Weight, or GWT of the horsebox or trailer. To avoid breaking the law, you will need to do some basic calculations and subtract the un-laden weight of the horsebox or trailer (how much it weighs empty) from the MAM – this will give you what is known as the Payload (the weight you can put in the trailer).

To put it simply, if you have a 7.5 tonne horsebox and it weighs 5.6 tonnes empty (before you have loaded anything into it), you can load 1.9 tonnes into the vehicle (this is known as your payload). It’s important to remember that 7.5 tonnes is the most the vehicle can weigh when fully loaded and not the amount of weight you can load into it!

Many people are shocked when they find out just how much their horsebox or trailer weighs before their horse has even stepped inside. The best way to find out the unladen weight of your vehicle is to take the vehicle empty (but with a full tank of fuel) to your nearest weighbridge. Once you know how much your vehicle weighs when empty and have worked out your payload you will then need to work out the weight of everything you want to put in the vehicle.

The table below gives you an idea of how quickly the weights can add-up using the example of the 7.5 tonne lorry above:


Weight (KG)

Payload remaining (KG)




Horse 1



Horse 2









Hay & Feed



The figures used in the table are real world weights taken from a weighing exercise. You can see that even on what many regard as a 'big box', the potential for getting things wrong is high.

Remember, overloading is regarded as an 'absolute offence' by the authorities, effectively one to which there is no defence. If detected, the vehicle will be prohibited from further movement until the excess weight is removed and a Fixed Penalty Notice or a court summons may follow.

Their Safety is your Responsibility #HBSW

You can show your support for the campaign and help to get #HBSW trending. Plus, you can view the whole Horsebox Safety Week video collection on our YouTube channel.

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