Maryland Route 108 is a state highway in the U.S. state of Maryland. The highway runs 34.23 miles (55.09 km) from MD 27 in Damascus east to MD 175 in Columbia. MD 108 is an S-shaped highway that winds through northern Montgomery County and central Howard County. The highway connects the Montgomery County communities of Laytonsville, Olney, Sandy Spring, and Ashton with the Howard County villages of Highland and Clarksville. MD 108 serves as the northern edge of Columbia and connects several of the planned community's suburban villages.

Maryland Route 27 is a state highway in the U.S. state of Maryland. Known for most of its length as Ridge Road, the highway runs 39.17 miles (63.04 km) from MD 355 in Germantown north to MD 30 in Manchester. MD 27 follows a ridge that separates several watersheds in northern Montgomery County and Carroll County. The highway connects Germantown and Manchester with Damascus in far northern Montgomery County; Westminster, the county seat of Carroll County; and Mount Airy, which lies at the junction of Carroll, Frederick, Howard, and Montgomery counties and where MD 27 intersects Interstate 70 (I-70)/U.S. Route 40.