The trunkline then heads southeast to Napoleon, where the road then turns south and heads towards Brooklyn, part of the Irish Hills area of Lenawee County, a region known for its scenery. The road serves as main street for downtown Brooklyn as well as the primary thoroughfare for drivers headed to Michigan International Speedway. M-50 curves around the north and east side of the race track before intersecting US 12 in Cambridge Junction. After crossing US 12, the road passes between several lakes of the Irish Hills area including Washington, Little Stony and Marrs lakes before continuing on its southeasterly journey towards Tecumseh.