This study of Swedish road and rail project performance challenges understanding of project success and presents findings that run counter to the widely held position that transport infrastructure delivery performance and outcomes are persistently poor. Both road and rail investments proved economically profitable and were typically delivered to budget, evidence that questions theory claiming optimism bias and malicious agency dynamics such as strategic misrepresentation are endemic in decision-making during planning and persistently cause poor project performance. Summary findings on the performance of Swedish transport infrastructure projects are: 93% of road projects achieved intended benefits, 86% returned positive net present value, and cost overrun was typically 2.7%. Road projects typically achieve a net present value of 1.6 against an estimate of 0.6. 70% of rail projects achieved intended benefits, 63% returned positive net present value, and typical cost performance was -1.8% underrun. This contribution opens new avenues for research by scholars to explain this apparent success and why some projects, even in Sweden, fail.