The sum does not include the cost of expenses incurred during the visits.
A seven-strong team from SPT, headed by chief executive Gordon MacLennan, travelled to Canada and Europe to assess companies tendering for contracts to upgrade the Subway.
The first trip in December involved visits to Canada, Spain and London, while the second in February took them to Denmark, Switzerland and Australia.
In 2010, then chief executive Ron Culley quit in the wake of a £120,000 expenses and travel scandal.
However, SPT has defended the decision to send seven employees on the fact-finding missions. It said the transport body is in the middle of a £288m upgrade of the Subway which will result in state-of-the-art driverless trains.
A spokesman said the findings would help save the taxpayer millions of pounds. He added: "SPT is progressing with an extensive Subway modernisation programme.
"The next stage includes the purchase of a new fleet of trains, a new signalling and control system and platform screen doors to replace an aging system and deliver a more frequent, reliable and flexible service to our customers while driving down maintenance costs."
Before SPT undertakes such a substantial upgrade, it needs to carry out detailed technical, operational and financial evaluation of the companies tendering for the work, in accordance with European procurement rules, the spokesman said.
He added: "These required a number of staff with significant expertise to visit multiple locations at the request of companies bidding. That was undertaken over a short period but involved very long days and has been extremely beneficial.
"Given the level of investment and future proofing decisions about to be made, it was imperative these visits took place."