You are the best person to judge your own safety if you have a breakdown.
However, the following points should be borne in mind when deciding what action to take. Remember - prevention is always better than a cure. Ensure your vehicle is regularly serviced, carry out checks yourself from your manufacturers handbook and make sure you have sufficient fuel for each journey.
Don't ignore warning lights - keep an eye on your dashboard and always stop at a safe place to carry out basic checks (consult your handbook if you are not sure what is wrong).
Use your senses: listen for unusual noises, or feel for strange vibrations. If you think something is abnormal, slow down until you find a safe place to stop, before seeking advice. If you have to stop – don't panic! Use the hard shoulder or a lay-by where possible, away from moving traffic. If you are unable to exit the traffic, stop as far to the right as you can, switch on your hazard lights and place your warning triangles behind and in front of your vehicle.
When exiting the car, do so from the passenger side, away from moving traffic and ensure all other occupants do so also. Make sure that the driver and each passenger are wearing their reflective jacket.
Consider your pets; in most circumstances it is safer to leave animals in the car – but make sure windows are open wide enough for ventilation but not enough to allow them to escape. Where possible, ensure drinking water is available.
Find a safe spot for your passengers - ideally behind a barrier and away from moving traffic.
Once everyone is safe, contact your breakdown cover provider or call a recovery company.
Leave the passenger door unlocked so you can quickly access the vehicle if you feel unsafe, and please remember that being hit by moving traffic is the most significant risk at a breakdown. So only return to the vehicle if you feel threatened, returning to a place of safety outside as soon as you can. If you can't get to a safe place, call the police. If there is nowhere safe outside the vehicle for passengers to wait, and there is a strong chance your vehicle could be struck, then call the police straight away with your location. If you have to remain in the vehicle keep your seatbelt on.