In rail terminology, a railway turntable or wheelhouse is a device for turning railway rolling stock, usually locomotives, so that they can be moved back in the direction from which they came. Naturally, it is especially used in areas where economic considerations or a lack of sufficient space have served to weigh against the construction of a turnaround wye. In the case of steam locomotives, railways needed a way to turn the locomotives around for return trips as their controls were often not configured for extended periods of running in reverse and in many locomotives the top speed was lower in reverse motion. In the case of diesel locomotives, though most can be operated in either direction, they are treated as having "front ends" and "rear ends" (often determined by reference to the location of the crew cab). When a diesel locomotive is operated as a single unit, the railway company often prefers, or requires, that it be run "front end" first. When operated as part of a multiple unit locomotive consist, the locomotives can be arranged so that the consist can be operated "front end first" no matter which direction the consist is pointed. Turntables were also used to turn observation cars so that their windowed lounge ends faced toward the rear of the train.
Early wagonways were industrial railways for transporting goods—initially bulky and heavy items, particularly mined stone, ores and coal—from one point to another, most often to a dockside to be loaded onto ships. These early wagonways used a single point-to-point track, and when operators had to move a truck to another wagonway, they did so by hand. The lack of switching technology seriously limited the weight of any loaded wagon combination.
The first railway switches were in fact wagon turnplates or sliding rails. Turnplates were initially made of two or four pieces of wood, circular in form, that replicated the track running through them. Their diameter matched that of the wagons used on any given wagonway, and they swung around a central pivot. Loaded wagons could be moved onto the turnplate, and rotating the turnplate 90 degrees allowed the loaded wagon to be moved to another piece of wagonway. Thus, wagon weight was limited only by the strength of the wood used in the turnplates or sliding rails. When iron and later steel replaced stone and wood, weight capacity rose again.
However, the problems with turnplates and sliding rails were twofold. First, they were relatively small (often no more than 1 yard (0.91 m) in length), which limited the wagon length that could be turned. Second, their switching capacity could only be accessed when the wagon was on top of them and still, which limited the total capacity of any wagonway. The railway switch, which overcame both of these problems, was patented by Charles Fox in 1832.
As steam locomotives replaced horses as the preferred means of power, they became optimised to run in only one direction for operational ease and to provide some weather protection. The resulting need to turn heavy locomotives required an engineering upgrade to the existing turnplate technology. Like earlier turnplates, most new turntables consisted of a circular pit in which a steel bridge rotated. The bridge was typically supported and balanced by the central pivot, to reduce the total load on the pivot and to allow easy turning. This was most often achieved by a steel rail running around the floor of the pit that supported the ends of the bridge when a locomotive entered or exited. The turntables had a positive locking mechanism to prevent undesired rotation and to align the bridge rails with the exit track. Rotation of the bridge could be accomplished manually (either by brute force or with a windlass system), popularly called an "Armstrong" turntable, by an external power source, or by the braking system of the locomotive itself, though this required a locomotive to be on the table for it to be rotated.
The turntable bridge (the part of the turntable that included the tracks and that swivelled to turn the equipment) could span from 6 to 120 feet (1.8 to 36.6 m), depending on the railway's needs. Larger turntables were installed in maintenance facilities for longer locomotives, while short line and narrow gauge railways typically used smaller turntables. Turntables as small as 6 feet (1.83 m) in diameter have been installed in some industrial facilities where pieces of equipment are small enough to be pushed one at a time by humans or horsepower.
In engine maintenance facilities, a turntable was usually surrounded, in part or in whole, by a roundhouse. It was more common for the roundhouse to only cover a portion of the land around a turntable but fully circular roundhouses exist, such as these preserved roundhouses:
Miskolc Tiszai railway station retains an active turntable as of December 2021.
There was a turntable at the Talaguppa end of the Shimoga-Talaguppa railway, and one at Howbagh Railway Station near Jabalpur on the Balaghat-Jabalpur Narrow Gauge Line. Both were used to turn the railbuses serving on these lines. After railbuses were replaced by MEMUs, turntables were dismantled.
In 2012, Mumbai Metro One, the BOT operator of the Mumbai Metro Line 1, announced that it had procured turntables to be used on the Rapid Transit system.
The Israel Railway Museum, Haifa, has a turntable made by Metropolitan Carriage, Wagon & Finance Company, Old Park Works, Wednesbury. It was found buried in the grounds of the Israel Defense Forces History Museum, on the site of the old Jaffa railway station yard.
Like most ex-socialist countries of Eastern Europe, Romania still has several turntables in operational use. One can even see twin turntables, each with their own 180 degree roundhouse, like for one example at Timisoara.
In Sri Lanka, most turntables which were used in the steam area have been abandoned. Most were situated at the major railway yards like Kandy, Galle, Nanu Oya, Anuradhapura, Maho, Galoya, Trincomalee, Batticaloa, Polgahawela Jnc, Badulla, Puttulam, and Bandarawela and depots in Dematagoda 2no. and Maradana. All turntables in Sri Lanka Railways were operated manually. They were used to turn some rolling stock and non-dual cab locomotives. Most turntables were later scrapped, though some have been preserved in museums.
In Britain, where steam hauled trains generally have vacuum operated brakes, it was quite common for turntables to be operated by vacuum motors worked from the locomotive's vacuum ejector or pump via a flexible hose or pipe, although a few manually and electrically operated examples exist. The major manufacturers were Ransomes and Rapier, Ipswich and Cowans Sheldon, Carlisle. The GWR was the railway company that built several tables for its own use; there is little evidence any other companies did so.
Due to the asymmetric design of many locomotives, turntables still in use are more common in North America than in Europe, where locomotive design favors configurations with a controller cabin on both ends or in the middle. In San Francisco, US, the Powell cable car line uses turntables at the end of the routes, since the cable cars have operating controls at only one end of the car. The Long Island Rail Road still has a turntable and roundhouse at the Richmond Hills yard.
Several working examples remain, many on heritage railways in Great Britain, and also in the United States. Some examples include:
The following are in storage, awaiting installation at UK sites:
New build turntable. Hitachi Rail Europe's rolling stock plant at Newton Aycliffe in County Durham has an 80 tonne locomotive turntable and a bogie test turntable; supplied by Lloyds British Somers Group in 2016.
The former Chicago, Milwaukee, St. Paul & Pacific (Milwaukee Road) in Janesville, Wisconsin. Used now by the regional Wisconsin & Southern
In the United States, when deciding liability for turntable accidents, most state courts followed the precedent set by the United States Supreme Court in Sioux City & Pacific R.R. v. Stout (1873). In that case, a six-year-old child was playing on the unguarded, unfenced turntable when his friends began turning it. While attempting to get off, his foot became stuck and was crushed. The Court held that although the railroad was not bound by the same duty of care to strangers as it was to its passengers, it would be liable for negligence "if from the evidence given it might justly be inferred by the jury that the defendant, in the construction, location, management, or condition of its machine has omitted that care and attention to prevent the occurrence of accidents which prudent and careful men ordinarily bestow."
In the case of Chicago B. & Q.R. Co. v. Krayenbuhl (1902), a four-year-old child was playing on an unlocked, unguarded railroad turntable. Other children set the turntable in motion, and it severed the ankle of the young child. The child's family sued the railroad company on a theory of negligence and won at trial. The Nebraska Supreme Court held that the railroad company may have been liable for negligence after considering the "character and location of the premises, the purpose for which they are used, the probability of injury therefrom, the precautions necessary to prevent such injury, and the relations such precautions bear to the beneficial use of the premises." However, the Supreme Court reversed the trial court's decision based on an improper jury instruction as to the evidence.
Accidents to locomotives sometimes occurred. For example, if the turntable was incorrectly set and a locomotive was accidentally started or failed to stop, it might fall into the turntable pit.
On rare occasions, a turntable would spin too fast during high winds, as happened at Garsdale (Settle–Carlisle line) in the UK c.1900. At this very exposed location, this was resolved by surrounding the turntable with a wooden stockade made from old sleepers. [specify]
Stations housing large numbers of engines may have more than one turntable:
A lever was installed at both ends of the bridge and the table was moved by hand, a method popularly called "Armstrong."