They believe ministers will use objections and other hurdles to effectively shelve several projects, although Transport Scotland has only admitted to one being put on hold by lack of money.
Those believed to be at risk are claimed to be the upgrading of the twisty upper Loch Lomond section of the A82 between Tarbet and Inverarnan, and junction improvements at Laurencekirk on the A90 in Aberdeenshire.
The source described the A82 scheme as “difficult and very expensive … Transport Scotland will never say it’s shelved, but it will progress at a snail’s pace”.
They said the Laurencekirk project would be delayed by objections.
Meantime, improvements to the A737 at Beith in North Ayrshire “won’t happen any time soon because there is no money”.
However, there are said to be fewer funding doubts over other schemes such as replacing the Sherriffhall roundabout bottleneck on the Edinburgh City Bypass as it is part of the Edinburgh City Region Deal.
Transport Scotland said: "We are committed to upgrading the A82 between Tarbet and Inverarnan. While there is still a lot of development work to be carried out, which is being informed by our enhanced understanding of the specific complexities associated with improving this iconic route, we continue to push forward the preparation stages.
"We continue to push the A90/A937 Laurencekirk junction improvement scheme through the statutory process. Four objections were received during the statutory consultation period, including one from Aberdeenshire Council, and we continue to work with objectors to resolve concerns where possible.
"Should we be unsuccessful in removing all objections, a public local inquiry may be required. Delivery of the scheme itself can only commence if it is approved under the relevant statutory procedures, at which point a timetable for its progress can be set.
“The A737 improvements had completed statutory processes and is progressing through necessary governance procedures. Whilst the Scottish Government remain committed to taking the project forward, procurement will commence when sufficient funding is available to support its construction. This will remain under active consideration during the regular reviews of future budgets and funding availability.”