There is an embankment as it ascends the rest of the Lincoln Cliff at Fulbeck Hilltop Plantation, and follows a former country lane the east of Fulbeck. It meets the former route (with access for "Pottergate Road" to Wellingore, and the A607) and passes across Fulbeck Heath. At Cranwell and Byard's Leap, it re-enters North Kesteven at the line of the north-south Ermine Street (now the Viking Way). The road used to briefly follow Ermine Street southwards to Byard's Leap with its cafe, and then eastwards to the current route at the B1429 junction. The road now passes slightly further to the north, with a right turn for the B6403, and a left turn for the B1429 for RAF Cranwell. In North Rauceby, it passes along the southern edge of the airfield. There is a crossroads for Cranwell, to the left, and North Rauceby, to the south. At Windmill plantation, the road has been straightened, entering the parish of Sleaford. There is a service station and transport cafe on the left hand side. It meets the north-south A15 at the "Holdingham Roundabout", near the "Jolly Scotchman" (on the B1518 - the former route). There is the Sleaford Little Chef, the Sleaford Travelodge, and the TOTAL "Holdingham Service Station". On the former route to Sleaford there is a McDonald's and the Texaco "Hockmeyer Motors". Sleaford was bypassed by the A17 on 27 March 1975, when opened by Joseph Godber. The section from the A15 to the A153 had earlier been opened on 14 November 1973. It is the only substantial section of dual-carriageway on the route, and the main opportunity to overtake caravans and lorries. There is the grade-separated "Bone Mill Junction" with the A153, which shares the route from Holdingham, and the B1517 for Sleaford. It crosses the Peterborough to Lincoln Line, then the River Slea and the Spires and Steeples Trail. East of here to the road's eastern terminus, the landscape is flat. At Kirkby la Thorpe it meets the former route from Sleaford, near the "Queens Head". The former route has a 13 ft 9in low (railway) "Boston Road Bridge", another important reason for building the bypass.