The road starts as an exit on the Grimston Bar interchange on the
A64 on the outskirts of York. It heads north east pass the turnings for
Murton,
Dunnington and Holtby within the first couple of miles. The first settlement that lies upon the road is
Gate Helmsley. From here the road gradually turns in an easterly direction until it is required to cross the
River Derwent at
Stamford Bridge. The bridge lies north east to south west at the point where there used to be a fording point. On exiting the town, the road returns to a north east direction to follow the route of the old Roman road. On the next section there is a turning northward toward the hamlets of
Buttercrambe and
Scrayingham at which point it turns easterly again. This is closely followed by a staggered junction further on with an exit south towards
Full Sutton and north to
Skirpenbeck. There are also turnings soon after to the south for
Youlthorpe and north to
Bugthorpe. Just south of the hamlet of
Garrowby the road takes a sharp turn south and then back east at the foot of Garrowby Hill. The hill is the highest point on the
Yorkshire Wolds and was the subject of a
painting by
David Hockney. The road up the hill covers , rising from to at an average gradient of 4.8%. Part way up the hill, is the southerly turn off toward
Bishop Wilton. Shortly after this junction an emergency stopping track can be seen on the downward side of the road. Consisting of gravel and sand, this is intended for vehicles to use in the event of a mechanical problem. There are several places where the road has been widened to allow slower traffic ascending or descending to pull to the left and allow faster vehicles to pass. In the next , there are junctions with the routes to
Great Givendale and
Pocklington to the south and
Thixendale to the north. At a dip and curve in the road known as Stone Dale, the road once more goes in a north east direction. The A166 next runs through
Fridaythorpe. On exiting the village, it meets the
B1251 road to Bridlington, which is designated as a
Scenic Route. Travelling in an easterly direction, the road follows an ancient
green lane until it reaches the village of
Wetwang. Either side of the village the road intersects the
B1248 Beverley to
Malton road. The road continues to
Garton-on-the-Wolds, where it is met by the
B1251 heading north west to
Sledmere. From here it turns south east to its junction with the
A614 Driffield By-pass. Only junctions with classified designations are included in the table below. ==Gallery==