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A dog loose in a car is a distraction for the driver and a hazard to everyone in the vehicle if the car stops suddenly. The Highway Code deals with it in one rule. This article sets out what that rule says, how the four options it lists differ, and what the equipment adds to a dog's running costs.
What Rule 57 says
Rule 57 of the Highway Code says that when you are in a vehicle you should make sure dogs or other animals are suitably restrained so they cannot distract you while you are driving. The rule goes on to say the restraint should also stop them injuring you, or themselves, if you stop quickly. The same rule names the ways to do it: a seat belt harness, a pet carrier, a dog cage or a dog guard.
The rule does not name a product or a standard. "Suitably" is a judgement about your dog and your car, which is why the choice below depends on the size of the dog and the layout of the vehicle.
The four options
A seat belt harness. PDSA recommends car safety harnesses for medium and large dogs. A harness fits around the dog's chest, back and shoulders and attaches to a rear safety belt. Measure your dog's chest at the widest point and compare it with the size chart for the model, and choose a Ad dog car harness with adjustment at the chest and the back, since a growing or filling-out dog will change size.
A pet carrier. Small dogs and cats travel in a carrier. A Ad rigid pet carrier needs to be sized to the animal and secured so it cannot slide about the car. PDSA notes that the back seat or boot can become dangerously hot, especially with a carrier, so check the temperature there before and during the journey.
A dog cage or crate. In an estate, hatchback or SUV, a cage in the boot keeps a dog away from the passengers. The cage has to fit the boot, so measure the boot floor, the height under the parcel shelf and the width between the wheel arches before ordering. A Ad boot dog crate for cars is bought to fit a specific space, so the measurements decide the model.
A dog guard. A guard divides the boot from the back seat, so the dog travels loose in the boot but cannot reach the passengers. A Ad boot dog guard keeps the cost and the bulk down. The limitation is that the dog is free to move about behind it, so it suits a dog that settles in the boot.
None of these is better in itself. The right one is the one that fits your dog and vehicle properly and gets used on every journey, including the five-minute ones.
Matching the option to the dog and the car
The sources above give one clear steer on size: harnesses for medium and large dogs, carriers for small dogs. Beyond that it comes down to the vehicle.
- A saloon or a car with a sloping rear window. There is no separate boot to fit a cage or guard, so a harness on the rear seat or a carrier secured on the seat is the practical route.
- An estate, hatchback or SUV. All four options are open, and the boot space decides between a crate and a guard.
- A small car with more than one dog. Plan one restraint for each dog rather than sharing one.
- A car shared with other drivers. Choose something that can be fitted in a couple of minutes, or it will be left out on the day it matters.
A quick test before the first real trip: fit the restraint at home, put the dog in it, and check that the dog can sit, lie down and breathe comfortably without the restraint riding up or catching on anything. Then take a short drive round the block before the long journey.
Buying with a measuring tape
Three checks before you pay for any of them:
- Size and weight range. Every listing states one. Use the dog's adult weight if you are buying for a puppy, and expect to replace a puppy-sized harness.
- What the listing says about testing. Some products are described as crash tested. Read who did the testing and what it covered, rather than treating the phrase as a guarantee.
- Your car. Measure the boot and the rear seat, and check where the belt anchors sit. A harness is only as good as the anchor point it clips to.
Restraint kit is a one-off spend that belongs in the first-year column, not the running costs. Get a quote or a listing price for the specific model before the dog arrives, and enter it under toys and accessories in the pet cost calculator alongside the bed, bowls and leads.
On the road
The same GOV.UK page collects PDSA and RSPCA advice for the journey itself:
- Keep journeys as short as possible, since long trips can be stressful, and plan regular rest breaks so the dog can toilet and stretch in fresh air.
- Carry plenty of drinking water and a bowl, even on short journeys. A Ad collapsible dog travel bowl takes up almost no room.
- Put the dog on the lead before you open the car doors. A spare Ad dog lead with a padded handle lives well in the glovebox.
- Do not let the dog put its head out of the window. PDSA gives eye injuries as the reason.
- Check the temperature in the back of the car, which can get dangerously hot.
If the car breaks down
The RSPCA advice on the page is that a dog should be removed from a broken-down vehicle if it is safe to do so. Keep the dog on the lead, and stand with it behind the crash barrier, as far from the roadside as possible. That is a reason to keep the lead where you can reach it without opening the boot.
Keeping the car usable
A dog that travels regularly will leave hair, mud and the odd accident behind. A Ad waterproof boot liner saves hours of cleaning, and it is cheaper to replace than the boot carpet. Neither the Highway Code nor the guidance above requires a liner, so treat it as a running-cost choice.
Taking the dog abroad by car
Travel to the EU has its own paperwork, and the pet owner's legal checklist covers the animal health certificate, the microchip and rabies timeline, and the validity windows. The restraint rules above apply on the way to the port or tunnel as much as on any other journey.