start on old road west of madingley rab about 580 yards west of the rab at a point 40yds east of comberton 2 sign and 49 yds west of road leading to comberton. proceed eastwards to madlingley rab where 1st. exit onto a428 to:- turn (5.18 mls) at cambourne flyover, turn right at 1st. rab, pass over a428 and right at next rab to re-enter onto a428 westbound. retrace a428 eastwards, bear left at a1303 cambridge road, pass over a428 to:- turn (10.18 mls) at madingley rab. retrace a428 eastwards to:- turn at cambourne flyover, turn right at 1st. rab, pass over a428 (15.10 mls) and right at next rab to re-enter onto a428 westbound. retrace a428 eastwards, bear left at a1303 cambridge road, pass over a428 to:- turn (20.09 mls) at madingley rab. retrace a428 eastwards to:- turn (25.02 mls) at cambourne flyover, turn right at 1st. rab, pass over a428 and right at next rab to re-enter onto a428 westbound. retrace a428 eastwards, bear left at a1303 cambridge road, pass over a428 to:- finish by turning left at madingley rab to finish at clearway end sign on road leading to madingley village.