Hard shoulders should be made available to Scottish commuters during rush hour, transport chiefs have argued.
An appeal has been made to Scottish Transport Secretary Stewart Stevenson as Transport Scotland plans a trial on part of the M77.
Buses will be allowed to use the hard shoulder during the morning rush on the northbound section of the motorway between junctions one and four.
A date has not yet been set for the trial, but a Transport Scotland spokeswoman said that after it had been evaluated, they "may then consider extending the concept to other priority users".
Tories, however, have accused the Scottish government agency of "watering the scheme down" by only allowing buses to take to the hard shoulder.
And transport spokesman Jackson Carlaw urged Mr Stevenson to introduce the scheme "for all vehicles on suitable sections of the M77, M8, A720, M74, M80 and other congested Scottish roads".
A Transport Scotland spokeswoman said: "We welcome support for our hard shoulder running pilot scheme on the M77.
"Subject to the availability of appropriate funds, and following evaluation of a successful bus pilot project, we may then consider extending the concept to other priority users."
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