Incident Sequence
The pilot reported a partial loss of engine power while in flight. After the initial power loss, he attempted to divert to an alternate airport for a landing. However, the engine continued to lose power, and the airplane was no longer able to maintain altitude. The pilot selected a portion of a highway as an emergency landing area. During the landing roll, the right wing struck an overhanging tree, causing the airplane to turn to the right and subsequently strike an embankment.
Damage
The airplane's wings and fuselage sustained substantial damage as a result of the impact with the tree and embankment.
Engine Inspection
A postaccident inspection of the engine revealed a broken intake valve on the number 3 cylinder, which likely contributed to the loss of engine power.