Complex sentence: The last major gap in the trail contains the northern section of Southington, the whole town of Plainville, which has an approved a feasibility study calling for a proposed route of approximately 4.4 miles in length including both off-road and on-road facilities.
Split into simpler sentences: The last major gap in the trail is the town of Plainville, which has just approved a feasibility study for the route of the trail through the town. The proposed route will be approximately 4.4 miles in length and will include both off-road and on-road facilities.