Driving a motorhome on a car licence – are you falling foul of the law?

Recently a friend of mine told me that he took hs motorhome to a weigh bridge and found that his vehicle was 50kg over the plated limit (3.5 tonnes). Bearing in mind that this was a motorhome kitted out for two people, when you consider the fact that many 6 berth, 6 belt motorhomes are advertised as being drivable on a B/Car licence it should lead you to consider how this works. The short answer? Generally it’s not that straightforward.

Many, maybe the majority, any motorhomes are under 3.5 tonnes when unloaded. This is known as the mass in running order (MIRO) so they can be plated or registered as being <= 3.5 tonnes and therefore technically can be driven on a car licence. However once we add accessories, supplies and food and water the vehicle is can be over 3.5 tonnes and is therefore illegal and not covered by insurance. 

MIRO, MTPLM and Payload – How to use these numbers to stay safe and legal

MIRO =Mass in Running Order. This is the weight of the vehicle with a 75kg driver and a 90% tank of fuel. This is what the manufacturer thinks the vehicle will weigh when it leaves the factory but this is only an estimate and the unladen weight should ideally be assessed at a weigh bridge to figure out your payload.

MTPLM = Maximum Technically Permissible Laden Mass. This is the maximum weight the motorhome is engineered/certified to carry and is generally determined by the weight each axle can tolerate. Sometimes this can be increased by uprating and will allow you to bring a greater amount of payload while still remaining safe and legal.

Payload is the difference between the mass in running order (MIRO) and the Maximum Technically Permissible Laden Mass (MTPLM). For example if you have a MTPLM of 3500kg and a MIRO of 3000kg your payload is 500kg.

My motorhome (MH) has a mass in running order of approximately 2950kg. When we add in the weight of all six occupants (approximately 150kg and increasing as the kids grow older and subtracting the weight of the driver which is already included in the MIRO) you might think that the remaining 400kg is plenty for the small amount of items one is likely to pack on holidays. But wait … there’s more. Most vehicles leave the factory with a set weight but get additional items added at the dealership to increase the usability of the vehicle, typically an awning, satellite dish and bike carrier. So this cuts into the already meagre 400kg available. Let’s guess for argument’s sake estimate that that this adds 50 kg. You are down to what might seem like a reasonable 350kg of available payload. Think again. I’ve done up a table of typical items we pack in our MH below and you’ll find that, depending on how you travel, you can easily exceed the available payload of your MH without even realising it. 

ItemWeight (kg)
2 x adults @ 75 kg*75
4x children @ 35kg140
Bicycles x 4 at 15kg /bike60
Water (onboard)50
Motorhome extras (OEM fitted)50
Levelling ramps5
Awning (tent style)35
Extra leisure battey (Varta LA 95)28
Gas cylinders (x2)25
Solar panels20
Clothes 2 x adults @ 10kg20
Clothes 4 x children @ 10kg40
TV system10
Bed clothes10
Bicycle rack10
Games, books etc10
Sat nav/head unit5
Cutlery, crockery5
Child seats5
Cleaning supplies5
Tablets etc3
Tables, chairs15
Electrical reel8
Outdoor cooker/BBQ8
Total687 kg
A table of items you are likely to bring on a trip and the approximate weight. For a family of 6 this pushes the extra weight you might be carrying to over 680kg. *The drivers weight at 75kg and 90% full fuel tank are added into the MIRO value provided by the motorhome manufacturer.

So, if we assume a fully kitted out holiday and add the above weight to our MIRO of 2950Kg above we will be running at a total weight of 3637kg. So 137kg over the weight limit for the vehicle. Add in a “modest’ amount of wine for the trip home and you start to hit against the design limits of the vehicle. We have yet to discuss overloading the front or rear axles …

Axle limits

Ok so it gets more complicated. Each axle has a maximum allowable weight so if you put the front or rear wheels on a weigh bridge the weight on each axle must not exceed the maximum axle weight. On our MH the maximum weight on the front axle is 1950kg and 2000kg on the rear. The total weight my motorhome is plated to carry (at present) is 3850kg but to carry the fully allowable weight I would have to have the weight distributed to ensure that there is no more than 1850kg on the front axle and 2000kg on the rear. Move something from the fridge to the front of the van and all of a sudden you’re exceeding one of the axle weights. In reality it’s never going to be possible to perfectly balance the weight to achieve the above but is is important to respect the limitations of the vehicle.

With the example of my MH being plated at 3850kg but being possible to register at 3500kg some might feel it reasonable to drive it at over 3500kg on a car licence knowing that the vehicle is engineered to function safely at the higher weight. So it’s not legal but it is not completely dangerous either. In fact if you are caught with your vehicle over the limit it’s only 1 penalty point (in Ireland at least), however you should not be permitted to continue your journey if your vehicle is overweight so it could being your holiday to a premature conclusion – or you might need to leave someone at the side of the road before continuing on… However if you exceed the overall weight limit or exceed an axle limit the vehicle’s handling or braking capacity can suffer, possibly at a level significant enough to cause an accident. Given that I’m writing about going on holidays with my wife and four children that’s just not a risk I (or you) should be willing to take.

Upgrading your vehicle’s weight limits

In the case of our MH it is plated to have a MTPLM of 3850kg. When we purchased it, it was registered at 3500kg and I re-registered it to 3850kg as I was sure we would exceed the 3500Kg. This was simple enough at import as I just selected the higher MTPLM however I do think it’s more difficult to uprate the weight limits after initial registration (or at least that’s my understanding of it).

I will soon be getting airbag suspension fitted to our MH which I understand will allow me to uprate the rear axle load to 2240kg and a MTPLM of 4090kg. I don’t think we’re going to hit those limits any time soon but as I will technically have the capability to uprate I will try and do so to try and figure out the system in Ireland and re-post at a later date.

Also don’t forget that the manufacturers will have limits on how much storage you can add to the rear garage, bike rack or other storage areas so regardless of how much you uprate your motorhome you will still have limitations on where you can distribute the extra weight.

Drivers licence requirements for motorhomes

So the 3500kg limit is significant because you can drive anything to to this limit on a standard car licence (B licence). This means you can legally drive anything from a smart car to a small truck as long as it doesn’t exceed 3500kg. I use the term ‘legally’ as the driving test doesn’t assess our ability to drive a particular vehicle so if you are comfortable driving a hatchback and sit your test in one it doesn’t necessarily mean you will have the spatial awareness to comfortably drive a small truck or motorhome. As soon as the maximum weight for the vehicle exceeds 3500kg you are required to have at a minimum a C1 licence which will cover you for anything up to 7500kg which is sufficient for the majority of motorhomes. If you intend driving a motorhome of over 7500kg you will need a ‘C’ licence. The C1 licence is sometimes referred to as an ambulance licence as the vehicle you do the test in is often sized the same as an ambulance whereas the C licence test is taken in a full sized rigid truck.

I felt it was a good idea to go for the C1/C licence not only to ensure I could keep everything legal and insurable, but to give me a chance to refresh my driving skills and prepare for driving a bigger vehicle. I would recommend it if you don’t have previous experience of driving commercial vehicles. It is a different style of driving and requires greater road awareness and planning than you would need when driving a car. It does cost money to get lessons for a C1/C licence but if it saves you the inconvenience (or worse) of being involved in an avoidable road traffic accident in an expensive motorhome it’s good value.

So how to keep it all safe and legal

If you travel with minimal kit and few people and your motorhome has a sizeable payload you may never have any issues with going on holiday and staying within the required weight limits. A trip to the weigh bridge when your van is fully loaded should confirm this and give you confidence should you happen across a police weigh station. If you are pushing close to the 3500kg mark or definitely north of it then a C1 licence might be the best way to go. The lessons will refresh and improve your driving skills and you will be able to legally drive anything up to 7500kg tonnes. This will give you the freedom to drive/purchase a bigger range of motorhomes or campers and will also allow you the freedom to uprate your existing vehicle if you have had to plate it to 3500kg due to your current licence.