md 170 begins at an intersection with md 175 (annapolis road) in odenton. the highway continues south as county-maintained piney orchard parkway, which leads to the odenton station on marc's penn line and the piney orchard community. md 170 heads north on telegraph road, which begins as a four-lane divided highway but reduces to a two-lane undivided road and passes through an industrial area. the state highway expands to a four-lane divided highway again shortly before its diamond interchange with md 32 (patuxent freeway). md 170 continues north as a two-lane road with a center left-turn lane that crosses severn run. the center turn lane ends as the highway approaches the center of severn. there, the highway intersects md 174, which heads west as reece road and east as donaldson avenue. md 170 expands to a four-lane divided highway as it approaches its single-point urban interchange with md 100 (paul t. pitcher memorial highway). the highway becomes an undivided four-lane road between md 100 and its intersection with md 176 (dorsey road) at harmans. the long ramp from westbound md 176 to northbound md 100 is unsigned md 170a.