Humberside International Airport
Ludborough (merging with the A16 road, near Louth)
It begins as a dual-carriageway and trunk road at the Balby Flyover junction with the A630 in Balby in Doncaster, under which runs the East Coast Main Line. It meets the A638 (former Great North Road) at the Sidings Roundabout then becomes Carr House Road, overlapping the A638. At the Racecourse Roundabout in Belle Vue, the A638 leaves to the right (former Great North Road), and the road becomes Leger Way, passing the Doncaster College for the Deaf on the left, and Doncaster Racecourse on the right. Near Intake, it becomes single carriageway, which it continues as for most of its length until it reaches Scunthorpe and also in Grimsby. On the right is Danum Academy (Danum is the Roman name for Doncaster) and Sandall Wood School, a special needs school. There is a roundabout with Armthorpe Road, with Wheatley Hills to the left and Wheatley Golf Club to the right. At the Sandall Park Roundabout the road meets its old route and becomes Thorne Road. At the Shaw Lane Roundabout it meets the A630, with exits for Shaw Lane Industrial Estate, and the road overlaps the A630 under a railway line. At the next roundabout, on the edge of Doncaster, the A630 leaves to the right, as a trunk road to the M18, with Edenthorpe Sainsbury's an exit to the south. The road, now without trunk (primary) status, passes Hungerhill School on the left near The Ridgewood pub and passes through Edenthorpe.
There is a roundabout for Armthorpe Lane (for Barnby Dun) and Hatfield Lane (for Armthorpe). It enters Dunsville as High Street, where it passes the Flare Path pub on the right (named after a nearby airfield's flare path) and Dunsville Primary School on the left and becomes Doncaster Road. It enters Hatfield, passing the Hatfield Chase pub and Ash Hill Academy. It becomes Manor Road near the Blue Bell pub and passes the parish church on the left and the library on the right near The Bay Horse Inn and Ingram Arms, becoming High Street and crosses the M18. It becomes Epworth Road and meets the A1146 to the left, near Hatfield Woodhouse, then meets the A614 from the right from Finningley. It becomes Tudworth Road and passes the Green Tree Brewers Fayre pub on the left, overlapping the A614 (for Hatfield Woodhouse) from the right at the Green Tree junction. There is a slip road for the M180 to the left, and it crosses the motorway and meets the large Tudworth Roundabout near Tudworth Hall Farm, where an eastbound exit from the M180 joins, the A614 exits (for Thorne), and the A18 continues in the direction to the right.
As High Levels Bank, it crosses a very flat landscape known as Hatfield Chase, often quite windy, in the same direction and destination as the nearby M180. It passes the Black Bull Inn on the right, then enters North Lincolnshire. It runs alongside the large North Engine Drain, with the former RAF Sandtoft nearby to the south, next to the M180. It passes the Lincolnshire Golf Club, to the right, at Hirst Priory near Belton. At Crowle, it meets the A161, close to junction 2 of the M180 and Crowle railway station. It crosses Pilfrey Bridge over the Three Rivers, passes Derrythorpe on the right near the T Bar Cafe and at Althorpe it passes the Dolphin Inn on a new section of road to the west of the village, and goes under the railway. It meets the B1392 (for Keadby) with the Keadby Power Station to the left, then past Althorpe railway station, running alongside the railway over the River Trent on the George V Bridge which opened in 1916, and is the furthest north crossing of the Trent. It passes through Gunness, crossing the B1216 (for Burringham) as Station Road and passes the Jolly Sailor. It briefly becomes a dual-carriageway where it meets the A1077 Scunthorpe ring road, and the M181 at the large Frodingham Grange Roundabout near the Gallagher Retail Park, a Tesco, a Travelodge, some fast food restaurants, The Old Farmhouse pub on the right, and Glanford Park. East of here to the A159 Ashby Road roundabout the road has trunk status. There is a roundabout for the retail park and then the Berkeley Roundabout, becoming Kingsway at the Esso Parkside Service Station.
It passes Kingsway golf club on the right and crosses the railway. It passes close to North Lindsey College on the right and meets the Queensway Roundabout for the trunk road A159 at Old Brumby, becoming the non-trunk dual-carriageway Queensway. It passes through New Brumby and Brumby Junior School on the left, then St Bernadettes RC Primary School on the right. It is crossed by the B1501 and at the Ashby Ville Roundabout it meets the A1029 from the town centre and an exit road for the Lakeside Retail Park and Morrisons near the steel works. In Gadbury Wood, the B1398 leaves to the right (to Kirton in Lindsey and Lincoln), where it ascends the northern section of the Lincoln Cliff. The road becomes single carriageway, and meets the Briggate Lodge Roundabout on the line of Ermine Street, for junction 4 for the M180, the trunk-road A15 and Forest Pines hotel and golf course. There are crossroads with the B1207 (for Scawby), then it crosses the M180 and meets the B1208 (for Broughton) from the left at Castlethorpe near the Arties Mill pub.
At Scawby Brook, there is a roundabout with the B1206 (for Scawby), with the Glanford Brigg Power Station in front on the former British Sugar plant, and the road enters Brigg to the left as Scawby Road, passing the Ancholme Leisure Centre on the right, and JET Brigg Service Station on the left near the bridge over the New River Ancholme, becoming Bridge Street passing the Nelthorpe Arms and Brocklesby Ox Inn, then Ancholme Way. The road bends sharply to the right and it passes through the town centre, with a Tesco on the right, as Barnard Avenue. There is a roundabout with the A1084 (for Caistor). It becomes Wrawby Road, and passes the Lower School site of the Sir John Nelthorpe School, which was the former Brigg Girls' High School. The B1206 (former A15) leaves to the left and the road enters Wrawby as Brigg Road passing the Jolly Miller on the left, and parish church on the right becoming Melton Road. It crosses a railway and there is a turn to the right for Barnetby and a T junction, with the main direction to the right. Turning to the left is a small section of the A18 at Wrawby Moor for the M180 junction 5, and the A180 at Barnetby Top Interchange, also crossed by the Viking Way. The A180 to Grimsby had originally been planned to be given the A18 designation.
It passes through Melton Ross, with a right turn for New Barnetby. The B1211 leaves to the left and it crosses the Grimsby railway near the Melton Ross Quarry, owned by Singleton Birch. It passes next to Humberside Airport, opposite which is Kirmington and an old Roman fort. At the B1210 (for Brocklesby) junction, the road heads to the right, entering Lincolnshire and the district of West Lindsey and passes through Great Limber near the New Inn as High Street. At an odd junction at Keelby, it meets the B1211 and heads to the right as Barton Street (a Roman road). Near Riby is a staggered junction at Riby Cross Roads with the A1173, and the road becomes a trunk road (until its terminus) then a dual-carriageway close to where it enters North East Lincolnshire.
There is a left turn for Aylesby, and at Laceby, the road meets the A46 Grimsby road, and heads straight on over the roundabout at the Irby Dale Service Station. The A18 used to continue eastwards from here along the present A46 into Grimsby, and now continues southwards over Welbeck Hill along the former B1431. It is crossed by the Wanderlust Way and there is a left turn for Barnoldby le Beck (and its Ship Inn). This section of Barton Street is situated to the east of an escarpment of the Lincolnshire Wolds. There is a small roundabout with the B1203 at Ashby Hill (for Brigsley and East Ravendale), and a left turn for Ashby cum Fenby. The boundary of Lincolnshire and North East Lincolnshire runs down the middle of the road for about 3 miles (4.8 km). There is a right turn for Wold Newton. The road re-enters Lincolnshire and the district of East Lindsey, close to Cadeby Hall. There is a private road to the right to Wyham. It turns to the left as Lincoln Gate, leaving Barton Street to the south, then to the right at Ludborough following the former A16 before the Ludborough bypass was built, then to the left as Pear Tree Lane and finally meets the A16 close to Utterby.
The last section between the junction with the A46 at Laceby and the junction with the A16 at Ludborough was designated by the Road Safety Foundation as the most dangerous in the country for car drivers drawing on collated data on the number of fatal and serious-injury collisions in 2010.
The A18(M) was a short motorway about 1 mile (1.6 km) long that connected the M18, from what is now junction 5 north of Hatfield to the A18. The A18(M) was built in 1972 but was redesignated after the M180 was built in 1978.
The western end of the M180 from M18 junction 5 to the junction 1 eastbound slip road was previously part of the A18(M). The eastbound slip road to the roundabout was the eastbound carriageway A18(M). About 0.5 miles (0.80 km) of the westbound A18(M) carriageway was abandoned when the M180 was built on a new alignment.