Auditor general Caroline Gardner found that the delivery of the Queensferry Crossing project has been managed effectively and delivered value for money, in a review of the scheme.
But more needs to be done to measure its wider benefits, such as cutting journey times and boosting economic growth, she said.
“Transport Scotland now needs to produce a clearer plan about how it will measure the success of the project's wider benefits, including its contribution to economic growth and improved public transport links,” Gardner said.
The bridge across the Firth of Forth came in almost £250m under budget when it opened a year ago, although its completion came eight months later than it was first estimated.
The audit report, published on Thursday, said that a key factor behind the success of the project was that the delivery team had “the right mix of skills and experiences”.
The watchdog added that the team has demonstrated strong, consistent leadership and had communicated well with contractors and stakeholder groups.
Transport secretary Michael Matheson said a full post-project evaluation was planned for later in the year.
He said: “While it is too early to complete a wide-ranging assessment evaluating the project’s outcomes, we accept the recommendations in the report and aim to carry out a full post-project evaluation in late 2018 detailing performance relating to journey times and traffic flows.
“This will include an assessment of the impact of improved network connections and junctions, and the project’s contribution to economic growth and exploring what further support can be offered to public transport providers to meet any future increase in demand for travel across the Forth.”
Gardner added that the public sector can learn from the way Transport Scotland managed the project and “it’s important that the good practice is shared more widely”.
