The A800 is nothing more than a short link to a semi-important through route from Bathgate. The number isn't even necessary for singular identification – except in Bathgate it is Balmuir Road, weaving out to hit the A801 (former A706) at a T-junction within two miles of leaving the A89 (former A8). The reason why it was ever considered to carry the rather important sounding A800 number is almost a mystery - but it is simply the first A road wholly in Zone 8 that the A8 met in 1922. Originally, the A800 operated with the A801 to form a north west - south east route between Falkirk and Bathgate, and by crossing the A706, it also connected with the county town of Linlithgow. Clearly, connecting these towns was important, and despite its diminutive length, the A800 remained the route of choice until the new A801 was opened.
The route starts at a roundabout in the centre of Bathgate and heads north, winding up Mill Road (the southern end of which has been realigned to the west) as it heads out of the town centre. At a mini roundabout, the now unsigned route doglegs to the right and then Mill Road becomes Balmuir Road as the route turns west and heads out of town. Houses and farms dot the roadside as it winds through the fields and then, with the A801 in view ahead, it suddenly makes a sharper right turn. After a short straight, the route turns westwards once more and comes to an end at Couston Crossroads, a staggered junction with the B8028 on the A801. Prior to the construction of this new road, the A800 continued an extra 100m or so westwards to end on the A706 where the B8084 now turns off the B8028.
The 1922 MOT Road List defines this route as: Bathgate - Junction with A706 near Bridge Castle