Crash-tested cages for the car boot
4pets PRO crash-tested dog cages

4pets of Switzerland is right at the forefront of innovation in crash-tested dog cages and crates.
Its TÜV approved PRO cage range has a patented high-tech rear panel that flexes when it's hit; absorbing and then releasing the kinetic energy in a controlled way to give the dog every possible chance of surviving a crash, whether the impact is from the front or the back of the vehicle. All parts of 4pets' PRO cages are designed to be both user-friendly and dog-friendly. They're based around an aluminium frame - much lighter to lift than steel - with fibreglass-reinforced plastic corners, and the sides and roof are made from a laminated fibreboard that won't get too cold in winter or too hot in summer.
Thule Allax crash-tested dog cages

The Thule Allax is a family of very well-designed, well-engineered and well-made TÜV approved crash-tested dog cages for use in the car boot; as with the 4pets cages, you need to choose a size that will fit in your vehicle.
Dog Ramps

Here's a simple solution for helping your dog in and out of the car. The 4pets EasySteps is a telescopic, lightweight, but super strong ramp. It's very easy to handle, and allows young and old dogs in particular to climb in and out of vehicles very easily, minimising the potential for muscle and joint damage to both dogs and their owners.
Alternative crash-tested products
4pets Caree crash-tested dog cages

For smaller pets the 4pets Caree is a state-of-the-art carrier for small pets weighing up to 15kg. It fits to the rear seat or passenger seat, either using a seatbelt or, for faster fitting and removal, using the ISOFIX latching points. It's designed for safety and has also passed TÜV's crash-testing regime. It's designed for ease of use, with a door on each side and a very cosy bed that's easily removed for hand washing.
SHERPA Harnesses
For pets who prefer to have a bit more space, a safety harness can be an excellent choice.
SHERPA harnesses were designed to meet child safety standards and have therefore been tested well beyond crash-testing requirements for dogs. You'll notice that a SHERPA harness is heavier duty than a standard dog harness; the large chest area distributes the weight much better than thinner harnesses, reducing the pressure on the dog's chest. SHERPA crash-tested car harnesses have a step-in design that makes them easy to fit and remove; they work with the existing seatbelts so the dog can sit, stand, or lie down, allowing them to make themselves as comfy as possible.