Extension B provides an overground Light Rail link of ~ 5.4 km from Coldhams Lane (where it links to Extension A) to Fulbourn, running parallel to, or sharing, the existing main eastern heavy rail line to Newmarket, Norwich and Ipswich. This would serve residents on the east side of Cambridge, for example in Cherry Hinton, as well as the Capital Park high-tech employment node (ARM, Syngenta etc), and the village of Fulbourn.
Extension B could provide fast access to centres of employment in Fulbourn, and connections from there to the Science Park, Cambridge West Campus, Addenbrookes / BioMedical Campus and the City centre. The costs of this line should be relatively modest, because it is mostly overground and would utilise the existing heavy rail alignment. A shared tram-train line might be possible, although the feasibility of this approach has not yet been investigated.