A new response system which aims to save more lives is to be piloted by the Scottish Ambulance Service.

Instead of using time targets which have been in place for 40 years, patients deemed to have life-threatening conditions will be prioritised.

People who have been injured in serious road traffic incidents or suffered conditions such as cardiac arrest will receive the fastest response.

In less urgent cases, call operators will be encouraged to speak to patients for longer to get a clearer picture of the kind of help they need.

The pilot scheme follows similar changes in Wales and parts of England which have led to faster response times for critically-ill patients.

It marks the first major change to the Scottish Ambulance Service's time-based targets system since 1974.

The system, which was developed after the examination of half a million emergency calls, will be introduced by the end of the year and piloted for 12 months.

The SAS has an eight-minute target for the call-outs classed as life-threatening but the new model will involve the introduction of three response categories.

Immediately life-threatening calls, such as a cardiac arrest, will maintain the eight-minute target; calls where a patient needs a fast response and transfer to a healthcare facility will be prioritised on the basis of clinical need and receive a blue-light response but there will be no time target; and other calls will be "managed safely at home" or by referral to GPs, NHS 24 or social care services.

Examples of immediately life-threatening calls include serious road traffic collisions, acute anaphylactic shock, patients who are unconscious and not breathing, and vulnerable patients such as pregnant women and young children.

Examples in the second category of response include patients experiencing chest pain or possible heart attack symptoms, people with breathing problems, symptoms of a stroke or a suspected serious fracture.

Pauline Howie, chief executive of Scottish Ambulance Service, said: "The new model is the result of the most extensive clinically-evidenced review of this type undertaken in the UK and focuses on improving patient outcomes, rather than simply measuring the time it takes to respond.

"It will allow us to respond faster to more patients with time-critical, immediately life-threatening conditions.

"In other situations, we will safely and more effectively identify and send the right resource first time for patients, resulting in better overall clinical outcomes.

"The focus on time-based targets for ambulance responses has changed little in around 40 years and does not take account of the advances made in clinical development of pre-hospital care."

Ms Howie said the service would consult with staff, patients and stakeholders throughout the pilot to make improvements.

A report on the success of the project, which has been supported by the British Heart Foundation, will be submitted to the Scottish Government at the end of the pilot.

Scotland's Chief Medical Officer, Dr Catherine Calderwood, said: "The Scottish Ambulance Service has undertaken a rigorous review of its clinical data, involving a full year of actual patient outcome data being analysed.

"What the analysis showed was that the current coding system does not always accurately identify some patients' conditions as immediately life-threatening.

"And that other codes were getting an eight minute response, although the patient's condition had no time critical response requirement.

"I am persuaded by the extensive clinical evidence that the Scottish Ambulance Service has put forward and know that patient safety is at the heart of these changes."

Scottish Ambulance Service chairman, David Garbutt, said that saving more lives and improving care was "fundamental".

"This new model is a significant step forward in delivering the board's vision for continuous improvements in the quality of care for our patients," he said.

Dr Mike Knapton, associate medical director at the British Heart Foundation, said: "In the event of a cardiac arrest, time is critical and the best way to get professional help is to call 999 without delay.

"I'll look forward to seeing the results of this pilot to ensure that heart patients continue to receive timely and quality care."