Interstate 495 begins as the direct continuation of Route 25 at the intersection with Interstate 195 in West Wareham. It starts as a two-lane highway in both directions. It gets the third lane during the interchange with Route 24. The junction includes the unusual transition of shrinking from the six-lane Route 25 to the four-lane interstate, due to the third lane of Route 25 joining to and from I-195. The road heads roughly northwest, passing through the towns of Rochester and Middleborough (where the road meets U.S. Route 44) as a four-lane highway before entering Bristol County, crossing the Taunton River at Raynham. There, it becomes a six-lane highway just southeast of the Route 24 interchange (which is actually in neighboring Bridgewater).