The original route to carry the B924 number in 1922 was what is now part of the B9157. Following Bridge Street, Pratt Road and Abbotshall Road around the south west of Kirkcaldy, the route was upgraded to A-road status (becoming part of a rerouted A907) before 1932. The history behind this, however, is a little confusing. The A907 had originally followed a more northerly course into Kirkcaldy, which became unclassified when the A907 was rerouted. However, following this change the B924 survived as a short route to the west leading into Aberdour, with the A907 following the route that connected the two former B924 routes. It is therefore a plausible theory, currently without any mnapping evidence to support it, that the B924 was extended to Aberdour prior to the A907 being re-routed.
The road has been downgraded once more since the 1970s, but the original number had already been reused and so both of the ex-B924 routes are now numbered B9157, the western one having briefly carried the A987 number.