A 'terminal headshunt' is a short length of track that allows a locomotive to uncouple from its train, move forward, and then run back past it on a parallel track. Such headshunts are typically installed at a terminal station to allow the locomotive of an arriving train to move to the opposite end of (in railway parlance, 'run around') its train, so that it can then haul the same train out of the station in the other direction (assuming, of course, that it is a locomotive equipped to run in either direction; for older, one-way equipment such as steam locomotives and cab unit locomotives, a wye or turntable needs to be provided to physically turn the engine around, as well as a run-around track).
Found primarily on metro systems, rapid transit light rail networks, and tramways, a 'reversing headshunt' allows certain trains or trams to change direction, even on lines with high traffic flow, whilst others continue through the station. Typically there will be two running lines, one for each direction of travel, and the headshunt will be positioned between the two running lines, linked to both by points. Although most trains will pass through the station and continue in the same direction, an individual train may be directed into the reversing headshunt, before exiting onto the other running line, in the opposite direction of travel. This procedure allows a greater frequency of trains on a city-centre section of the line, and reduced frequency on the suburban sections, by allowing certain trains to shuttle back and forth only on the city centre part, using the reversing headshunts to change direction within the flow of trains.
The term headshunt may also refer to shunting neck or 'shunt spur': a short length of track laid parallel to the main line for the purpose of allowing a train to shunt back into a siding or rail yard without occupying the main running-line.
A run round loop (or run-around loop) is a track arrangement that enables a locomotive to attach to the opposite end of the train. It is commonly used to haul wagons onto a siding, or at a terminal station to prepare for a return journey. This process is known as "running round a train".
Although a common procedure for passenger trains when the majority of them were locomotive-hauled, the maneuver is now becoming rarer on public service railways. Increased use of multiple unit and push-pull passenger services avoids the requirement for dedicated track and the need for railway staff to detach and reattach the locomotive at track level. However, on heritage railways run-round loops are still usually more or less necessary at each end of the running line, partly because train services are usually locomotive-hauled, and partly because the run-round operation gives added interest to visitors. This practice is still very common on Intercity services in Victoria, Australia.
Runaround tracks are used in freight rail service in order to back cars into spurs or to change directions to keep the locomotive at the front of the train for transport. In this case the runaround track must be as long as the longest set of cars that would be pulled. The locomotive leaves the cars on the runaround track or the main line, goes around, and hooks up to the other end of the train. It can then reverse the cars into a spur.
Stations which used to have run-rounds include:
- Edinburgh Waverley railway station; The terminal platforms of this station featured locomotive release roads between two main platforms, connected by a three-way point to the crossover from each platform line. ·  ·  ·  The same arrangement of a three-way point on a central release road was also installed at the now closed stations :
- St Ives railway station
- Matlock Riverside railway station, now closed
- Birmingham Moor Street. This station is on a confined site, so to save space the platform lines were equipped with traversers to allow locomotives to run round via the adjacent platform line (platforms 1 & 2) or an adjacent loop (platform 3).
- Withernsea, the terminal station on the now closed Hull and Holderness Railway. At this station, instead of a crossover or points the run round loop was accessed from a turntable at the end of the platform line and run round loop · . There was a similar arrangement at Ventnor and Bembridge railway stations on the Isle of Wight.
Stations which still have run-rounds include:
- Australia (all in regular loco-hauled passenger use unless otherwise indicated)
- Central railway station, Sydney
- Albury railway station
- Canberra railway station (run-around not in regular use)
- Southern Cross railway station (Melbourne)
- Shepparton railway station
- Bairnsdale railway station
- Geelong railway station
- South Geelong railway station
- Marshall railway station
- Warrnambool railway station
- Swan Hill railway station
- Seymour railway station
- Roma Street railway station (Brisbane) (not sure if run-around in use)
- Toowoomba railway station
- Charleville railway station
- Rockhampton railway station
- Longreach railway station
- Townsville railway station
- Mount Isa railway station
- Cairns railway station
- Kuranda railway station
- Adelaide Parklands Terminal
- Public Transport Centre (East Perth terminal)
- Darwin railway station
If a terminal station has or no longer has a run-round loop, trains are restricted to multiple units or Top and Tail trains.
Sometimes a terminal station has no run-round loops, the absence of which is overcome by coupling a relay engine to the rear to power the next out bound trip. The original engine of the arriving train shunts to the relay engine siding where it awaits the arrival of the second train, and so on. Examples in steam days include Fenchurch Street and Kingsgrove.
- Jackson, Alan A. (2006). The Railway Dictionary (4th ed.). Sutton Publishing Ltd. p. 298. ISBN 0-7509-4218-5.
- Ellis, Iain (2006). Ellis' British Railway Engineering Encyclopaedia. Lulu.com. p. 307. ISBN 978-1-8472-8643-7.
- Edinburgh Waverley station - Ordnance Survey 25" to the mile - published 1896
- Edinburgh Waverley station - NBR Co. plan - published ca. 1898 - zoomed in
- Edinburgh Waverley on OS town plan (1887) showing 3-way release crossover points between platforms
- Edinburgh Waverley on OS town plan (1894) showing 3-way release crossover points between platforms 2 & 3 and 4 & 5
- Manchester Central on OS 1:500 town plan (1888) showing 3-way release crossover points between platforms 1 & 2, 3 & 4 and 5 & 6
- Manchester Central station - Ordnance Survey 25" to the mile - published 1934
- Manchester Central station looking towards the buffer stops (Disused Stations in the UK)
- Manchester Central station from the buffer stops (Disused Stations in the UK)
- 1864 - 1:500 town plan (Disused Stations)
- Liverpool Exchange on OS 1:500 town plan (1890) showing 3-way release crossover points between platforms 4 & 5
- Preston Hendry, R., Powell Hendry, R., (1982) An historical survey of selected LMS stations : layouts and illustrations. Vol. 1 Oxford Publishing
- Leeds Central station from the buffer stops showing 3-way point for release crossovers
- Leeds Central on OS 1:500 town plan (1910) showing 3-way release crossover points between platforms 2 & 3
- "Moor Street Passenger Station". Warwickshirerailways.com. Retrieved 24 March 2013.
- "Moor Street Station: Ex-GWR 2-6-2T 'Prairie' No 6152 is seen standing on the traverser as it is being moved from platform 2 to platform 1 on the right". Warwickshirerailways.com.
- A locomotive at Moor Street being transferred to the run round loop for platform 3 (Warwickshirerailways.com)
- "Station Name: Withernsea". Disused Stations. Subterranea Britannica. 19 April 2019. Retrieved 8 March 2022.
- 1891 1:2,500 OS map showing the layout of Withernsea station (Disused Stations in the UK)