Belfast–Newry line

Due to the Belfast Grand Central enabling works, the line currently operates only from Newry to Lisburn. A rail replacement bus service runs from Lisburn to Belfast until the line reopens.

A small yard exists at Lisburn station, typically used by permanent way vehicles and, until recently, the storage of redundant stock. Lisburn is also the junction for the single-track Antrim branch, which runs adjacent to the double-track Newry line through the Lisburn suburbs, creating the illusion of triple-track. These lines pass under Thiepval Road and Causeway End Road in a deep cutting before reaching the former site of the second Knockmore halt, staggered across the Ballinderry Road bridge and demolished in 2014. After passing under the Knockmore Road, future site of Lisburn West railway station and site of the original Kockmore station, the Antrim Branch diverges to the right. Prior to 1956, this was also the junction for the Banbridge, Lisburn and Belfast Junction Railway's line to Hillsborough, Dromore, Banbridge and onwards to Castlewellan and Newcastle. This part of line runs through an industrial estate, with the Coca-Cola bottling plant to the right. The section between Lisburn and Moira is generally flat and straight. After crossing the Lissue Road on the level trains pass the former site of Damhead halt, and before reaching Moira will have passed other former halts at Broomhedge and Maze. The line then crosses the A26 Glenavy Road and enters Moira station.

Moira boasts the oldest extant railway building in Ulster, and along with Lisburn is an excellent example of restored GNR architecture. Immediately after leaving the station the line crosses the Lagan Canal on the Askew Bridge, and then runs parallel to the M1 motorway as far as Kilmore, where the railway passes under it. Kilmore is the site of the short-lived Pritchard's Bridge railway station, with the rest of the way to Lurgan being composed largely of agricultural land. Entering Lurgan from the north-east, the line crosses the Antrim Road and Lake Street on the level before passing under the Kilmaine footbridge and reaching Lurgan station.

Lurgan station was briefly known as Craigavon East for a time back in the 1970s. Immediately after the station, the line crosses William Street on the level and proceeds through the Lurgan suburbs, passing under the Eastway and running on a causeway between the two balancing lakes at Craigavon. Running behind Rushmere shopping centre, the line comes parallel with the Northway. It then passes under the M12 motorway and the site of the former Goodyear halt (Which served the nearby Goodyear Tire factory), and slightly further down the line, the site of the former Seagoe station, which was a temporary terminus during construction of the line to Portadown. The site of the first and third Portadown stations is passed, which today is a small maintenance yard with a siding. The line crosses its first, and only river- The Bann- and arrives at Portadown station.

The current (Fourth) Portadown station is on the same site as the second one, and was formerly the junction between the mainline and the lines to Armagh and Derry Foyle Road. For a time in the 1970s it was known as Craigavon West. Most non-Enterprise trains, save for couple of peak commuter services, terminate here. The line leaves Portadown by means of a 90° curve to the southeast, adjacent to Portadown South Sidings, and once free of the suburbs runs parallel to the Cusher River, Newry Canal and River Bann as far Moneypenny's Lock, where the latter leaves the railway and veers towards Gilford. Continuing alongside the Canal towpath, the line runs through agricultural surroundings as it passes the former site of Tanderagee station, closed in 1965, before reaching Scarva station.

Scarva was formerly the junction with the line to Banbridge via Laurencetown, which closed in 1955. The line continues out of Scarva station, still following the Newry Canal past Lough Shark and bypassing the village of Acton shortly before reaching Poyntzpass station.

Poyntzpass station retains a single siding, used by NIR as a loading point for ballast trains with stone brought in by road from a quarry near Banbridge. Poyntzpass is also home to the only GNR signal cabin still in its original location on NIR. The line continues to hug the Newry Canal, crossing it twice about halfway between Poyntzpass and Jerretspass. On the approach to Newry, the remains of Goraghwood railway station, once an important junction with the lines to Armagh and Warrenpoint, are passed, whilst the railway and canal part ways. The railway crosses the A28 and then the 18-arch Craigmore Viaduct, which takes it into Newry station.

Newry is the terminus of all local NIR trains, with the only trains extending further being the Enterprise and a daily Iarnród Éireann commuter service to Dublin. The line carries on south, crossing the A25 on MacNeill's Egyptian Arch. The embankment the railway is carried on soon becomes a cutting and the line is crossed by the A1 dual carriageway, the main road from the North to Dublin. From here the two run parallel as far as Cloughoge Chapel, where the railway diverges into another cutting before diving under the A1 again just north of Killeen. The railway then bypasses Meigh, in the shadow of Slieve Gullion, and passes the site of the long-closed station at Adavoyle. Finally, at Milepost 59 ¹/₂, the line crosses the border and becomes Iarnród Éireann's Northern Line.

Passengers can alight at Portadown, Scarva and Poyntzpass to access the towpath of the Newry Canal.

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  Craigmore ViaductinBessbrook near Newry.
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  Craigmore Viaduct with the Mournes in the background, seen from Bessbrook near Newry station.
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  Viaduct over the River Bann near Portadown.
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  The exGatwick Express rolling stock on the line at Goodyear near Seagoe.

• Northern Ireland Railways page on Belfast-Newry line
• Northern Ireland Railways page on Cross Border (Enterprise) line
• Northern Ireland Railways page on the Enterprise Service to Dublin Connolly