Highthorn Road starts at the A78 main road where the south pillars are located and then turns into the Beech Avenue shortly after passing over Millstonford Bridge. This area is called Highthorn due to the now demolished mansion house of Highthorn that is located about 300 meters south of the pillars.
The two pillars are made of solid sandstone and was once located about 200 meters further south but when Highthorn Road was realigned in the 1950s the pillars and road moved further North to where it is today.
The original road passed through the field and came out just prior to the bridge but no evidence exists of the road now except on old maps.
It has its own designated road number, that being U35, unlike an 'A' or 'B' road which are maintained by the regional authority 'U' roads are maintained at a local council level, that being North Ayrshire Council.