Investment company 3i Infrastructure said the sale of the freight rolling Eversholt Rail helped its full-year returns to increase at its highest level since its initial public offering (IPO) in 2007.Total return increased by 24.6% to £267m, which the company said was driven by the sale of Eversholt Rail and valuation gains in its European core investments.However, the group downgraded its return target from 10% to a "sustainable target" of 8% to 10% for the year. It explained the updated target is consisted with the sale of Eversholt Rail and the current returns from its core infrastructure and primary projects.Profits before tax jumped 275.7% to £266.8m, driving earnings per share up to 30.3p from 8.1p the year before.Despite a decline of 18.7% in investment income to £58.1m, investment return rose to £304.8m from £80.8m.3i blamed a low interest rate environment and higher prices of some infrastructure assets for the decline of projected returns.The group said these factors hurt its core infrastructure assets, making it "more challenging for the company to secure new investments at returns consistent with its existing targets".Due to increasing competitions for large core infrastructure assets, 3i started investing in "more attractive" risk-adjusted returns in other areas such as mid market core infrastructure and low-risk energy projects.It also announced it will pay an annual dividend of 7.25p per share in 2016.Chairman Peter Sedgwick, who announced on Tuesday his intention to resign from the board by the end of the year, said: "The board is announcing a revised total return target, providing increased flexibility for future investment, as well as a new dividend policy designed to maintain dividend progression each year for our shareholders."In combination with the exceptional return generated from the sale of our interest in Eversholt Rail, this facilitates a return of capital to shareholders, while maintaining a good level of liquidity for new investment."Shares were down 0.06% to 163.4p on Tuesday at 08:54.