Maryland Route 3 (MD 3), part of the Robert Crain Highway, is the designation given to the former alignment of U.S. Route 301 (US 301) from Bowie, Maryland, United States, to Baltimore. It is named for Robert Crain of Baltimore. It is unique in Maryland in that it has a business route and a truck route which do not connect to their parent; however, the business route is also a part of the Robert Crain Highway. MD 3's current orientation is vestigial from the construction of Maryland's freeway system.
Route description
thumb|left|View south along MD 3 at MD 32 near Millersville
MD 3 begins within the modified cloverleaf interchange of US 50 and unsigned I-595 (John Hanson Highway) and US 301 (Robert Crain Highway) in Bowie, Prince George's County. Within the interchange, US 301 heads south on Crain Highway and east along US 50; meanwhile, MD 3 heads north on Crain Highway, a four-lane divided highway. A short distance after beginning, the route comes to a partial cloverleaf interchange with Belair Drive, containing continuing connections from the US 50/US 301 interchange. Past here, the road runs north through wooded residential areas before the median widens and it bends to the north-northeast, continuing through forested areas with a few businesses. MD 3 continues northeast and the median narrows, with the road widening to eight lanes as it comes to an intersection with MD 450. At this point, MD 450 heads northeast for a concurrency with MD 3 along a six-lane divided highway, running through wooded areas and coming to a bridge over the Patuxent River.
thumb|right|View south along MD 3 near MD 175 in Millersville
Upon crossing the Patuxent River, the road enters Anne Arundel County and continues northeast, with MD 450 splitting from MD 3 by turning to the east. MD 3 continues north along Crain Highway into Crofton, passing between woodland to the west and residential subdivisions to the east. The road heads into a commercial area and comes to an intersection with the northern terminus of MD 424. At this point, the route turns to the northeast and the median widens to include businesses in the center. MD 3 heads into Gambrills and runs through more commercial areas. The median narrows as the road passes to the southeast of the Waugh Chapel Towne Center shopping center and runs between businesses to the northwest and residential neighborhoods to the southeast. The median widens again and the route narrows to four lanes at the St. Stephen's Church Road intersection, passing through a mix of fields, woods, and businesses. The road comes to an intersection with the eastern terminus of MD 175 in Millersville before it heads northeast through woodland. MD 3 comes to its northern terminus at a modified cloverleaf interchange with I-97 and the eastern terminus of the MD 32 freeway. I-97 passes under MD 3 and occupies its median for a very short distance, with MD 3 ending at ramps merging into northbound I-97. The roadway of MD 3, however, continues for a minor distance longer, the southbound carriageway turning and crossing underneath I-97 to join with the northbound on the east side of the Interstate, and continuing north as Veterans Highway, running parallel to I-97 and providing access to MD 178.
MD 3 Bus. is the only business route in the Maryland state highway system that no longer connects with its parent route. This is due to the construction of a bypass freeway, which took over the MD 3 designation as it was built; MD 3 Bus. was designated for the present business route as it was constructed. However, the freeway was later designated as I-97, and MD 3's mainline was truncated to the point at which the freeway and MD 3 deviated onto different routes, south of MD 3 Bus. Despite this, several locations on I-97 have "TO MD 3" signs posted.
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