Rail profile

Strap rail and spike

The earliest rails were simply lengths of timber. To resist wear a thin iron strap was laid on top of the timber rail. This saved money as wood was cheaper than metal. The system had the flaw that every so often the passage of the wheels on the train would cause the strap to break away from the timber. The problem was first reported by Richard Trevithick in 1802. The use of strap rails in the United States (for instance on the Albany and Schenectady Railroad c. 1837) led to passengers being threatened by "snake-heads" when the straps curled up and penetrated the carriages.[2]

T-rail was a development of strap rail which had a 'T' cross-section formed by widening the top of the strap into a head. This form of rail was generally short-lived, being phased out in America by 1855.[9]

Plate rail was an early type of rail and had an 'L' cross-section in which the flange kept an unflanged wheel on the track. The flanged rail has seen a minor revival in the 1950s, as guide bars, with the Paris Métro (Rubber-tyred metro or French Métro sur pneus) and more recently as the Guided bus. In the Cambridgeshire Guided Busway the rail is a 350 mm (14 in) thick concrete beam with a 180 mm (7.1 in) lip to form the flange. The buses run on normal road wheels with side-mounted guidewheels to run against the flanges. Buses are steered normally when off the busway, analogous to the 18th-century wagons which could be manoeuvered around pitheads before joining the track for the longer haul.

A cross-section through the Great Western Railway's baulk road, made with bridge rail

Bridge rail is a rail with an inverted-U profile. Its simple shape is easy to manufacture, and it was widely used before more sophisticated profiles became cheap enough to make in bulk. It was notably used on the Great Western Railway's 7 ft 1⁄4 in (2,140 mm) gauge baulk road, designed by Isambard Kingdom Brunel.

Cross section of Barlow rail as used by Sydney Railway Company

Barlow rail was invented by William Henry Barlow in 1849. It was designed to be laid straight onto the ballast, but the lack of sleepers (ties) meant that it was difficult to keep it in gauge.

Cross section of new flat bottomed rail

Flat bottomed rail is the dominant rail profile in worldwide use.

Flanged T rail (also called T-section) is the name for flat bottomed rail used in North America. Iron-strapped wooden rails were used on all American railways until 1831. Col. Robert L. Stevens, the President of the Camden and Amboy Railroad, conceived the idea that an all-iron rail would be better suited for building a railroad. There were no steel mills in America capable of rolling long lengths, so he sailed to the United Kingdom which was the only place where his flanged T rail (also called T-section) could be rolled. Railways in the UK had been using rolled rail of other cross-sections which the ironmasters had produced.

In May 1831, the first 500 rails, each 15 feet (4.6 m) long and weighing 36 pounds per yard (17.9 kg/m), reached Philadelphia and were placed in the track, marking the first use of the flanged T rail. Afterwards, the flanged T rail became employed by all railroads in the United States.

Col. Stevens also invented the hooked spike for attaching the rail to the crosstie (or sleeper). At the present time, the screw spike is being used widely in place of the hooked spike.

Vignoles Rail as used for the London and Croydon Railway in 1839

Vignoles rail as used for the Birmingham and Gloucester Railway in 1840

Vignoles rail is the popular name of the flat-bottomed rail, recognising engineer Charles Vignoles who introduced it to Britain. Charles Vignoles observed that wear was occurring with wrought iron rails and cast iron chairs upon stone blocks, the most common system at that time. In 1836 he recommended flat-bottomed rail to the London and Croydon Railway for which he was consulting engineer. His original rail had a smaller cross-section than the Stevens rail, with a wider base than modern rail, fastened with screws through the base. Other lines which adopted it were the Hull and Selby, the Newcastle and North Shields, and the Manchester, Bolton and Bury Canal Navigation and Railway Company.[10]

When it became possible to preserve wooden sleepers with mercuric chloride (a process called Kyanising) and creosote, they gave a much quieter ride than stone blocks and it was possible to fasten the rails directly using clips or rail spikes. Their use spread worldwide and acquired Vignoles's name.

The joint where the ends of two rails are connected to each other is the weakest part of a rail line. The earliest iron rails were joined by a simple fishplate or bar of metal bolted through the web of the rail. Stronger methods of joining two rails together have been developed. When sufficient metal is put into the rail joint, the joint is almost as strong as the rest of the rail length. The noise generated by trains passing over the rail joints, described as "the clickity clack of the railroad track", can be eliminated by welding the rail sections together. Continuously welded rail has a uniform top profile even at the joints.

Double-headed rail on the Mid-Norfolk Railway

In late 1830s Britain, railway lines had a vast range of different patterns. One of the earliest lines to use double-headed rail was the London and Birmingham Railway, which had offered a prize for the best design. This rail was supported by chairs and the head and foot of the rail had the same profile. The supposed advantage was that, when the head became worn, the rail could be turned over and re-used. In practice, this form of recycling was not very successful as the chair caused dents in the lower surface, and double-headed rail evolved into bullhead rail in which the head was more substantial than the foot.

Bullhead rail was the standard for the British railway system from the mid-19th until the mid-20th century. For example, in 1954 bullhead rail was used for 449 miles (723 km) of new track and flat-bottom for 923 miles (1,485 km).[11] One of the first British Standards, BS 9, was for bullhead rail - it was originally published in 1905, and revised in 1924. Rails manufactured to the 1905 standard were referred to as "O.B.S." (Original), and those manufactured to the 1924 standard as "R.B.S." (Revised).[12]

Bullhead rail is similar to double-headed rail except that the profile of the head of the rail is not the same as that of the foot. Bullhead rail evolved from double-headed rail but, because it did not have a symmetrical profile, it was never possible to flip it over and use the foot as the head. Therefore, because the rail no longer had the originally-perceived benefit of reusability, it was a very expensive method of laying track. Heavy cast iron chairs were needed to support the rail, which was secured in the chairs by wooden (later steel) wedges or "keys" which required regular attention.

Bullhead rail has now been almost completely replaced by flat-bottom rail on British railways, although it survives on the national rail system in some sidings or branch lines. It can also be found on heritage railways, due both to the desire to maintain an historic appearance, and the salvage and reuse of old track components from the main lines. The London Underground continued to use bullhead rail after it had been phased out elsewhere in Britain, but in the last few years has there been a concerted effort to convert its track to flat-bottom rail.[13] However, the process of replacing track in tunnels is a slow process due to the impossibility of using heavy plant and machinery.

Cross section of a grooved tram rail

Difference in form and profile of the wheel and the rail of a train (left, blue) and a tram (right, green). See Railway wheel flange

Where a rail is laid in a road surface (pavement) or within grassed surfaces, there has to be accommodation for the flange. This is provided by a slot called the flangeway. The rail is then known as grooved rail, groove rail, or girder rail. The flangeway has the railhead on one side and the guard on the other. The guard carries no weight, but may act as a checkrail.

Grooved rail was invented in 1852 by Alphonse Loubat, a French inventor who developed improvements in tram and rail equipment, and helped develop tram lines in New York City and Paris.[14] The invention of grooved rail enabled tramways to be laid without causing a nuisance to other road users, except unsuspecting cyclists, who could get their wheels caught in the groove. The grooves may become filled with gravel and dirt (particularly if infrequently used or after a period of idleness) and need clearing from time to time, this being done by a "scrubber" vehicle (either a specialised tram, or a maintenance road-rail vehicle). Failure to clear the grooves can lead to a bumpy ride for the passengers, damage to either wheel or rail and possibly derailing.

The traditional form of grooved rail is the girder guard section illustrated to the left. This rail is a modified form of flanged rail and requires a special mounting for weight transfer and gauge stabilisation. If the weight is carried by the roadway subsurface, steel ties are needed at regular intervals to maintain the gauge. Installing these means that the whole surface needs to be excavated and reinstated.

Block rail is a lower profile form of girder guard rail with the web eliminated. In profile it is more like a solid form of bridge rail, with a flangeway and guard added. Simply removing the web and combining the head section directly with the foot section would result in a weak rail, so additional thickness is required in the combined section.[15]

A modern block rail with a further reduction in mass is the LR55 rail[16] which is polyurethane grouted into a prefabricated concrete beam. It can be set in trench grooves cut into an existing asphalt road bed for Light Rail (trams).[17]

Rails are made in a large number of different sizes. Some common European rail sizes include:

In the countries of the former USSR, 65 kg/m (131 lb/yd) rails and 75 kg/m (151 lb/yd) rails (not thermally hardened) are common. Thermally hardened 75 kg/m (151 lb/yd) rails also have been used on heavy-duty railroads like Baikal–Amur Mainline, but have proven themselves deficient in operation and were mainly rejected in favor of 65 kg/m (131 lb/yd) rails.

Weight mark "155 PS" on a jointed segment of 155 lb/yd (76.9 kg/m) "Pennsylvania Special" rail, the heaviest grade of rail ever mass-produced

Cross-section drawing showing measurements in Imperial units for 100 lb/yd (49.6 kg/m) rail used in the United States, c. 1890s

New York Central System Dudley 127 lb/yd (63.0 kg/m) rail cross section

The American Society of Civil Engineers (or ASCE) specified rail profiles in 1893 for 5 lb/yd (2.5 kg/m) increments from 40 to 100 lb/yd (19.8 to 49.6 kg/m). Height of rail equaled width of foot for each ASCE tee-rail weight; and the profiles specified fixed proportion of weight in head, web and foot of 42%, 21% and 37%, respectively. ASCE 90 lb/yd (44.6 kg/m) profile was adequate; but heavier weights were less satisfactory. In 1909, the American Railway Association (or ARA) specified standard profiles for 10 lb/yd (4.96 kg/m) increments from 60 to 100 lb/yd (29.8 to 49.6 kg/m). The American Railway Engineering Association (or AREA) specified standard profiles for 100 lb/yd (49.6 kg/m), 110 lb/yd (54.6 kg/m) and 120 lb/yd (59.5 kg/m) rails in 1919, for 130 lb/yd (64.5 kg/m) and 140 lb/yd (69.4 kg/m) rails in 1920, and for 150 lb/yd (74.4 kg/m) rails in 1924. The trend was to increase rail height/foot-width ratio and strengthen the web. Disadvantages of the narrower foot were overcome through use of tie plates. AREA recommendations reduced the relative weight of rail head down to 36%, while alternative profiles reduced head weight to 33% in heavier weight rails. Attention was also focused on improved fillet radii to reduce stress concentration at the web junction with the head. AREA recommended the ARA 90 lb/yd (44.6 kg/m) profile.[18] Old ASCE rails of lighter weight remained in use, and satisfied the limited demand for light rail for a few decades. AREA merged into the American Railway Engineering and Maintenance-of-Way Association in 1997.

By the mid-20th century, most rail production was medium heavy (112 to 119 lb/yd or 55.6 to 59.0 kg/m) and heavy (127 to 140 lb/yd or 63.0 to 69.4 kg/m). Sizes under 100 lb/yd (49.6 kg/m) rail are usually for lighter duty freight, low use trackage, or light rail. Track using 100 to 120 lb/yd (49.6 to 59.5 kg/m) rail is for lower speed freight branch lines or rapid transit; for example, most of the New York City Subway system track is constructed with 100 lb/yd (49.6 kg/m) rail. Main line track is usually built with 130 lb/yd (64.5 kg/m) rail or heavier. Some common North American rail sizes include:[19]

Some common North American crane rail sizes include:

Some common Australian rail sizes include:

• 50 kg/m and 60 kg/m are the current standard, although some other sizes are still manufactured.[20]
• Some larger U.S. sizes are used on northwest Western Australian iron ore railways.