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Optimising ambulance conveyance rates and staff costs by adjusting proportions of rapid-response vehicles and dual-crewed ambulances: an economic decision analytical modelling study
  1. Colin Ridyard1,
  2. Murray Smith1,
  3. Robert Spaight2,
  4. Graham Richard Law1,
  5. Aloysius Niroshan Siriwardena3
  1. 1 Community and Health Research Unit, University of Lincoln, Lincoln, UK
  2. 2 Clnical Audit and Research Unit, East Midlands Ambulance Service NHS Trust, Nottingham, UK
  3. 3 Lincoln School of Health and Social Care, University of Lincoln, Lincoln, UK
  1. Correspondence to Dr Colin Ridyard, CaHRU, University of Lincoln, Faculty of Health Life and Social Sciences, Lincoln, LN6 7TS, UK; mhsa08{at}


Aim To model optimum proportions of dual-crewed ambulances (DCAs) and rapid-response vehicles (RRVs) in Ambulance Trusts with a view to generating a policy brief for one Ambulance Trust and a modelling tool for other Trusts on the strategic procurement and allocation of emergency vehicle (EV) resources.

Methods Historical EV assignments for 12 months of emergency calls in 2019 were provided by an NHS Ambulance Trust and analysed for backup, see and treat, and patient to hospital conveyance. Unit costs were derived for paramedics and technicians using Agenda for Change pay rates. Time cycles were assigned for RRV and DCA attendances and unit costs assigned to these. Information was put into a decision analytical model to estimate the costs and numbers of vehicles attending incidents based on relative proportions of available RRVs and DCAs.

Results Of 711 992 calls attended by 837 107 EVs, 514 766 (72.3%) required at least one emergency department conveyance. The rate of conveyance was significantly lower when RRVs arrived first on the scene. 27 883 out of 529 693 (5.3%) DCAs first arriving at an incident required some backup, and this was also factored into the model. Modelling demonstrated high conveyance rates were counterproductive when increasing the relative proportions of RRVs to DCAs. For example, with conveyance rates of 65%, increasing the RRVs increased the cost and numbers of vehicles attending per incident. At lower conveyance rates, however, there was a levelling around 30% where it could become cost-effective to increase the relative proportions of RRVs to DCAs.

Conclusion At current overall conveyance rates, there is no benefit in increasing the relative proportions of RRVs to DCAs unless additional benefits can be realised that bring the conveyance rates down.

  • emergency ambulance systems
  • emergency responders
  • costs and cost analysis
  • cost efficiency

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Data may be obtained from a third party and are not publicly available.

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Data availability statement

Data may be obtained from a third party and are not publicly available.

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  • Handling editor Caroline Leech

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  • Contributors CR was the main author and guarantor, and carried out the research based on ideas put forward by ANS, RS and MS. Contributing ideas to the methods and analysis came from ANS, RS and MS with particularly useful information on statistics from GRL. All contributors reviewed the results and helped formulate the conclusions.

  • Funding This study was funded by QR Strategic Priorities Fund 2020-21, University of Lincoln.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.