Vast stretches of West Lothian are now covered by a reduced 20mph speed limit, brought in under emergency measures as part of the response to the Covid pandemic last year.
But frustration at the slow speed is causing drivers to take more risks, which driving instructors say is making it increasingly difficult to teach learner drivers safely.
And they also warned the limit made it more difficult to teach students gear changes – and could be adding to environmental pollution.
One instructor, Ronnie Malcolm, said: “There have been countless occasions where I have witnessed dangerous overtakes by other drivers while my pupil has been observing the 20mph limit.
“Most of these overtakes will have necessitated the overtaking vehicle to be going significantly faster than the original 30mph limit. Most of these 20mph limits have actually created more dangerous situations than they have prevented.”
Mr Malcolm said fellow instructors had similar stories and faced similar dangerous situations.
One said: “My pupil was in a 20 zone, on a straight road, and about to take the next right turn. The vehicle behind us was a large van and then a long queue of traffic behind that.
"The car behind the van had obviously had enough of us sticking to the speed limit and decided to overtake.
"Obviously they hadn’t seen that we were signalling to turn right though. I had to take the wheel to stop my pupil turning into the path of this car, who was now on the wrong side of the road overtaking two vehicles at a junction.
”It really gave her a fright and shook her up at the very end of her lesson.”
Instructors also said that maintaining a crawling speed through all types of road does not allow them to teach learners how to use the gears.
A West Lothian Council spokesperson said: “The temporary 20mph speed limits in West Lothian are in place as part of the Spaces for People programme, and will be removed in line with Scottish Government Covid-19 guidance.”