US project-based business travel accounted for an estimated $45 billion in lodging, transport, dining, and other expenses last year, according to the Global Business Travel Association (GBTA).

The term refers to travel that revolves around a project, has both a start and end date, and has a duration of at least four nights or has a recurring component.

Project-based travel represented about 15 per cent of all business travel spending and 12 per cent of all business trips in 2017, according to a GBTA report prepared in cooperation with Intercontinental Hotels Group.

Top destinations for project-based business travel included New York, Los Angeles, Las Vegas, Chicago, and San Francisco.

The study found that business travellers spent more ($679) on project-based trips than for other types of business travel ($533), due in part to longer average stays and higher trip budgets.

Lodging costs on project-based trips are 142 per cent higher than for other types of business travel.

Project-based business travelers spent a total of $15.9 billion on lodging, $14.6 billion on air transportation, $7.0 billion on food & beverage, $1.8 billion on entertainment, $4.2 billion on ground transportation and $1.9 billion on retail.

Manufacturing, real estate, and professional services spent the most on project-based travel, which is especially prevalent in the construction industry.