London Ambulance Service NHS Trust uses OS Places API for out of area look ups

Using the OS Places API allows the London Ambulance Service NHS Trust to use flexible search methods for call handlers including full address, partial address

London Ambulance use AddressBase Premium data to locate addresses when responding to 999 calls. When an address is provided to the call handler, they can verify the address using AddressBase Premium, which also provides the grid reference. The grid reference and the address enable the ambulance responders to navigate quickly to the right location.

  • OS Places API


During the Coronavirus pandemic ambulance service call handlers received unprecedented and sustained volumes of 999 calls. Services across the country support each other by buddying up and answering each other’s overflow emergency calls.

Currently when an emergency call comes through to London Ambulance Service from outside their area, the call handler simply notes down the address and passes it to the buddy ambulance service to respond. There is no way for the call handler to verify and check the address, because like most ambulance services, London only has AddressBase Premium for their own area. Without coordinates the London Ambulance Service map application is not helpful.

Not being able to check the address and grid reference can cause serious delays in getting to the right location. This can become more serious if the 999 call has already been finished and the caller is not available to reconfirm an incorrectly recorded address.

Ambulance on route to an incident


Loading and managing AddressBase Premium data for a large area is time consuming and takes up data storage. OS Places API requires no downloading or storage and contains up to date addresses for the whole of the UK. Therefore, London Ambulance Service was able to implement OS Places API into their system for out of area address look ups, simply by entering a character prefix with the address search. This API provides the correct address, the grid reference and Unique Property Reference Number (UPRN). The UPRN can be linked to other data in the future if required.

The API allows flexible search methods for call handlers including full address, partial address (with missing postcode or town), door number and postcode and postcode alone. Multiple search results are displayed to the call handler and as each result has OS supplied coordinates the map will centre. This allows the call handler to question the caller with more confidence regarding questionable address formats and locations.


Using OS Places API takes away the need to load and manage AddressBase Premium for the whole of GB. This is time consuming and also requires a lot of storage.

OS Places provides the most up to date address information without the need to load change only updates or new epochs of AddressBase premium.

Having the ability to verify and visualise the ‘out of area’ addresses whilst speaking to the caller gives the call operator staff confidence; and provides significant time savings for the ambulance trying to locate the patient. If an address is unverified then the ambulance could be sent to the wrong location causing unnecessary delays in treating the patient.

"When an unverified address is sent to the Ambulance Service required to respond, the vehicle could be sent to a wrong location or the address may not be found at all. The time taken attempting to verify the provided address description can have a detrimental effect on the person requiring medical attention. The benefits of using the OS Places API is significant for avoiding unnecessary delays in mobilising the resources to the incident location."

John Downard, Head of IM&T Applications

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Products and solutions featured in this study

  • OS Places API

    Perform accurate geocoding and reverse geocoding with our secure, scalable, and resilient address API.