Trooper Troy C. Wood of the state Highway Patrol said it was unclear what caused Todd Allen Spencer, 50, to run off the road to the left on a 2012 Harley-Davidson.
Wood did say there is the possibility of a medical condition.
The crash occurred in the northbound lane of the interstate near the 176 exit in Northampton County when Spencer ran off the shoulder and struck a guardrail around 6:45 tonight.
His riding companions declined comment.
