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Research and Projects

PenCHORD - What are the factors that most influence demand for ambulances in South West England?

Who is involved?

Theme: PenCHORD
Status: Complete


Demand for ambulance services is growing year-on-year nationally, but the driving factors behind this increase are poorly understood. In collaboration with experts from the South West Ambulance Service NHS Foundation Trust (SWASFT), we identified those factors directly or indirectly contributing to demand for ambulances in South West England. We captured these influencing factors in a simulation model and then removed them, one by one, in order to estimate their impact on ambulance demand per year. From this, we were able to identify which factors are the biggest contributors to demand for ambulance services in the region.


  • To identify the direct and indirect factors that contribute to demand for ambulance services in South West England.
  • To use simulation modelling to estimate those factors that contribute most to demand for ambulance services in South West England.

Project Activities

We built a map of factors that potentially influence demand for ambulances using a mixture of expert opinion and information from the literature, obtained in collaboration with the PenCLAHRC Evidence Synthesis Team. This map was then translated into a simulation model parameterised with data relevant to the population of South West England.

We used a simulation modelling method called System Dynamics, which is typically used to develop models of large-scale “whole systems” and the flows between components in these systems. Here, we applied the method to capture the flow between a population who hasn’t yet called for an ambulance and one who has, as well as the factors that influence this rate of flow (demand for ambulances). By removing each factor in turn, we could determine which of these were estimated to have the biggest impact on demand for ambulances.


Outputs and Impact

The model estimates that the prevalence of falls in the elderly population is by far the most significant contributor to ambulance demand in South West England and is estimated to be over three times more significant than other known sources of high demand, such as referrals from the 111 service. In addition, the increased predisposition of those with mental health problems to use ambulance services is also estimated to be a significant influence on ambulance demand.

Based on these results, we recommended that an increased focus on falls prevention strategies, along with approaches to better understand the reasons why those with mental health problems use ambulances more frequently, could be extremely beneficial in reducing an increasing burden on ambulance services in South West England.

We presented these results to executives at SWASFT and the Lead Commissioners for South West England. As a result of our findings, the Lead Commissioners asked commissioning groups across the South West to escalate falls prevention and mental health strategies to be priority issues in their future commissioning plans.

Further details about this research have been published in the Journal of Paramedic Practice.

Read more in our news story featuring this project.

This work also featured in local television and radio news reports. A video of the BBC Spotlight report can be viewed below:

Listen to audio clips of the Radio Exe features below:

Related publications

Chalk D, Black S, Pitt M. Which factors most influence demand for ambulances in South West England? Journal of Parametric Practice 2016, 8:7

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Others Involved

Evidence Synthesis Team