Car Safety for Dogs: Highway Code Rule 57 Explained

Highway Code Rule 57 states that dogs and other animals must be suitably restrained in a vehicle so they can't distract or injure you, or themselves, during a sudden stop. Acceptable restraints named in the rule are a seat belt harness, a pet carrier, a dog cage or a dog guard. It's a "should", not a "must", so it isn't a direct offence in itself, but ignoring it can still land you in serious legal trouble.

This is a plain-English explainer, not legal or veterinary advice. If your dog is anxious or sick in the car, your vet can advise on settling them safely for journeys.

What Rule 57 actually says

The wording is short: when in a vehicle, make sure dogs or other animals are suitably restrained so they cannot distract you while driving or injure you, or themselves, if you stop quickly. It then lists the four approved methods. Crucially, Rule 57 uses the word "should", which in Highway Code terms is advisory rather than a law you can be fined for breaking on its own.

So is it illegal to drive with an unrestrained dog?

Not directly, but here's the catch. Police can still penalise you for driving without proper control or for careless driving if an unrestrained dog distracts you, with on-the-spot fixed penalties and points, and far higher fines and a court appearance if it goes further. Advisory Highway Code rules are also routinely used as evidence in court to establish fault. On top of that, many car insurance policies can be invalidated if an unrestrained pet contributes to an accident, leaving you to foot the bill.

In short, "only advisory" does not mean consequence-free. An unrestrained dog is a genuine safety risk to everyone in the car.

The four approved restraints

• Seat belt harness. A crash-tested harness that clips to the seat belt anchor. Choose one that fits snugly across the chest, not the neck, and that's rated for your dog's weight. Best for dogs comfortable on the back seat.
• Pet carrier or crate. A secured carrier suits small dogs, cats and nervous travellers, keeping them contained and calm. Larger crates fixed in the boot work for bigger dogs.
• Dog guard. A barrier between the boot and the cabin stops a dog climbing forward. It's the lightest-touch option and is often paired with a harness for actual crash protection.
• Boot-fitted [dog car seats](/dog-car-seats) and booster seats give small dogs a secure, raised, restrained spot.

Weigh up which suits your dog in our comparison, Dog Car Seat vs Crate vs Seatbelt: Safest Way to Travel.

Choosing the right restraint for your dog

Size and temperament decide it. Small dogs and cats often travel best in a secured carrier or a raised booster on the back seat, where they feel enclosed and can see you. Medium and large dogs usually do better with a crash-tested seat belt harness or a fixed crate in the boot. Whatever you choose, never let a dog ride in the front with the airbag active, never restrain by the collar alone, and never let them put their head out of the window at speed.

For smaller breeds specifically, Best Dog Car Seat for Small Dogs (UK, Highway Code Friendly) covers the practical picks.

Fitting and using a restraint properly

The best restraint in the world does nothing if it's fitted wrong. A seat belt harness should be snug enough that you can fit two fingers under the straps but no more, sitting across the breastbone rather than the throat, with the tether short enough that your dog can't be flung forward into the seat in front. Check the harness is genuinely crash-tested, not just a walking harness with a seat belt loop, as the two are very different in a collision.

For crates and carriers, secure the unit itself so it can't slide or tip; a loose crate is a projectile of its own. Wedge it against seats or strap it down, and place it in the footwell or boot rather than on a seat where it could fall. Whatever the method, build your dog up to it with short, calm trips so the car becomes a relaxed place, not a stressful one.

Practical safety beyond the law

• Acclimatise gradually with short, calm trips and treats before any long journey.
• Never leave a dog in a parked car in warm weather, even briefly, as temperatures climb dangerously fast.
• Carry water and take breaks on long drives.
• Position the restraint so a sudden stop can't throw your dog into a seat back or window.
• Check the fit of harnesses regularly, as a loose harness offers little protection.

Suitably restrained isn't bureaucratic box-ticking. In a 30mph crash an unsecured dog becomes a heavy projectile, for itself and everyone in the car.

For more on travelling with your dog, browse the walk and travel range and the wider Dog Walking & Travel hub.