At the time, I asked Ash Denham, whose constituency includes the stretch of Gilmerton Road @IWRATS mentions why she voted against that amendment.
"As this amendment was to amend secondary legislation, it would be far more suited to being in secondary legislation itself, rather than having a bill provision further amend what is already an amended instrument."
This was not the reason Michael Matheson, the transport secretary, gave in the chamber when he explained why the SNP wouldn't be voting for it. He spoke instead about the need to consult the public, I think.