An Auckland company that helps ambulances reach emergencies post-haste has grown by a quarter in the last 12 months.

Optima Corporation produces software informing ambulance operators where they need to place vehicles and how many paramedics they need to service each part of a city.

The software analyses variables, such as traffic during a certain time of day, the weather and the road quality to work out where vehicles need to be to meet emergency response times in different suburbs or communities.

As traffic flow changes, the software feeds vehicles' updated response times back to an ambulance dispatcher, who can then work out where the vehicles should be moved to.

Optima chief executive Chris Mackay said the programs also allow authorities to plan for future demand.

"The model we use is a little like [video game] Sim City where they can do all these 'what if' scenarios, determine where they need to invest money and show evidence to funders, typically government, as to why they need existing or additional funds," he said.

As well as being used by St John in New Zealand, the software is gaining traction in the lucrative North American market, with Optima signing its latest contract in the US city of Denver.

The $500,000 deal is the 12th the company has made in the US and contributed to a 25 per cent increase in earnings over the past year. More specific details were not available as Optima had yet to officially inform shareholders.

While Mackay is pleased with the result, he said the North American market is worth US$1 billion ($1.24 billion) and predicted Optima could double its growth rate over the next 12 months.

While the company is securing contracts in Europe and the United Kingdom, Mackay said North America remains the main focus. Optima's growing number of "smart health" products continues the company's move away from the industry it worked with when founded 13 years ago by students and staff at the University of Auckland's engineering faculty.

In its early years the company provided software models for airlines. Its first project was a system to manage crew rosters for Air New Zealand, saving the airline $14 million a year.

Optima software is deployed in Europe, North America, Australia and New Zealand.