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The term ruling grade is usually used as a synonym for "steepest climb" between two points on a railroad. More simply, the steepest grade to be climbed dictates how powerful the motive power (or how light the train) must be in order for the run to be made without assistance. Even if 99% of the line could be run with a low-powered (and inexpensive) locomotive, if at some point on the line there is a steeper gradient than such train would be able to climb, this gradient "rules" that a more powerful locomotive must be used, in spite of it being far too powerful for the rest of the line. This is why special "helper engines" (also dubbed "Bankers") are often stationed near steep grades on otherwise mild tracks. It is cheaper than running a too-powerful locomotive over the entire track mileage just in order to make the grade, especially when multiple trains run over the line each day (to help justify the fixed daily cost of the helper operation).
In the 1953 edition of Railway Engineering William H. Hay says "The ruling grade may be defined as the maximum gradient over which a tonnage train can be hauled with one locomotive....The ruling grade does not necessarily have the maximum gradient on the division. Momentum grades, pusher grades, or those that must regularly be doubled by tonnage trains may be heavier." This means the "ruling grade" may change if the management chooses to operate the railroad differently.
Other things being equal, a train is harder to pull around a curve than it is on straight track because the wagons – especially bogie (2 axle) wagons – try to follow the chord of the curve and not the arc. To compensate for this, the gradient should be a little less steep the sharper the curve is; the necessary grade reduction is assumed to be given by a simple formula such as 0.04 per cent per "degree of curve", the latter being a measure of curve sharpness used in the United States. On a 10-degree curve (radius 573.7 feet) the grade would thus need to be 0.4% less than the grade on straight track.
Tunnels on steep gradients can present problems for air-breathing locomotives, such as steam locomotives and diesel locomotives. Poor ventilation in long or narrow tunnels can starve the locomotive of power. The solution is analogous to compensation for curvature and requires the gradient in the tunnel and for some distance on either side to be greatly reduced compared to the ruling grade. Unfortunately, the necessary compensation for gradient is not a simple equation, but is rather a trial and error process. Since one cannot build several tunnels to find out which one is best, it is useful to study existing tunnels with steep gradients.
Moisture from exhausts and springs can also make the rails slippery, and allowance may need to be taken for that as well.
In steam days Southern Pacific trains eastward across Nevada and Utah faced nothing steeper than 0.43% in the 531 miles from Sparks to Ogden—except for a few miles of 1.4% east of Wells. Trains would leave Sparks with enough engine to manage the 0.43% grade (e.g. a 2-10-2 with a 5500-ton train) and would get helper engines at Wells; the "ruling grade" from Sparks to Ogden could be considered 0.43%. But nowadays the railroad doesn't base helper engines at Wells so trains must leave Sparks with enough power to climb the 1.4%, making that the division's ruling grade.
As such, the term can be ambiguous; and is even more ambiguous if the ruling grade is impacted by the effect of a momentum grade. Overland Route trains from Sacramento, California to Oakland face nothing steeper than 0.5% on Track 1, the traditional westward track, but nowadays they might need to approach the Benicia bridge on Track 2, which includes 0.7 miles at about 1.9% on otherwise near-level track. Using this as an example, several issues arise on defining "ruling grade". One issue is whether a running start should be assumed and, if yes, the speed to assume. Another issue is the train length to assume, given that certain lengths exceed the length of the hill in question. And if a running start at some arbitrary speed is assumed, the calculated "ruling grade" will be different for locomotives having different power-vs-speed characteristics.
In the United States, Congress set the Standard Grade for railroads eligible for subsidies and grants in the 1850s. They took as that standard the one adopted by the Cumberland – Wheeling Railway, that grade being 116 feet per mile (2.2%). Later when charters were drawn up for the Canadian Pacific Railway in Canada and for the Union Pacific Railroad, the national governments imposed the Standard Ruling Grade on the two lines because each received federal assistance and regulation. (Vance, JE Jr.,1995)
A ruling grade is often found at a long climb up to a summit. Ideally, the cutting at the summit should be as deep as possible, such as at Shap, as this helps reduce the amount of climb and the steepness of the gradient. Alternately, a summit tunnel should be provided, such as at Ardglen.
A mountain railway is a railway that operates in a mountainous region. It may operate through the mountains by following mountain valleys and tunneling beneath mountain passes, or it may climb a mountain to provide transport to and from the summit.
A rack railway is a steep grade railway with a toothed rack rail, usually between the running rails. The trains are fitted with one or more cog wheels or pinions that mesh with this rack rail. This allows the trains to operate on steep grades above 10%, which is the maximum for friction-based rail. Most rack railways are mountain railways, although a few are transit railways or tramways built to overcome a steep gradient in an urban environment.
The grade of a physical feature, landform or constructed line refers to the tangent of the angle of that surface to the horizontal. It is a special case of the slope, where zero indicates horizontality. A larger number indicates higher or steeper degree of "tilt". Often slope is calculated as a ratio of "rise" to "run", or as a fraction in which run is the horizontal distance and rise is the vertical distance.
The Rimutaka Incline was a 3-mile-long (4.8 km), 3 ft 6 in gauge railway line on an average grade of 1-in-15 using the Fell system between Summit and Cross Creek stations on the Wairarapa side of the original Wairarapa Line in the Wairarapa district of New Zealand. The term "Rimutaka Incline" is sometimes used incorrectly to refer to other parts or all of the closed and deviated section of the Wairarapa Line between Upper Hutt and Speedy's Crossing, near Featherston. The incline formation is now part of the Remutaka Rail Trail.
The Cascade Tunnel refers to two railroad tunnels in the northwest United States, east of the Seattle metropolitan area in the Cascade Range of Washington, at Stevens Pass. It is approximately 65 miles (105 km) east of Everett, with both portals adjacent to U.S. Route 2. Both single-track tunnels were constructed by the Great Northern Railway.
The Big Hill on the Canadian Pacific Railway main line in British Columbia, Canada, was the most difficult piece of railway track on the Canadian Pacific Railway's route. It was situated in the rugged Canadian Rockies west of the Continental Divide of the Americas and Kicking Horse Pass. Even though the Big Hill was replaced by the Spiral Tunnels in 1909, the area has long been a challenge to the operation of trains and remains so to this day.
The Cromford and High Peak Railway (C&HPR) was a Standard-gauge line between the Cromford Canal wharf at High Peak Junction and the Peak Forest Canal at Whaley Bridge. The railway, which was completed in 1831, was built to carry minerals and goods through the hilly rural terrain of the Peak District within Derbyshire, England. The route was marked by a number of roped worked inclines. Due to falling traffic, the entire railway was closed by 1967.
Hillclimbing is a problem faced by railway systems when a load must be carried up an incline. While railways have a great ability to haul very heavy loads, this advantage is only significant when the tracks are fairly level. As soon as the gradients increase, the tonnage that can be hauled is greatly diminished.
A horseshoe curve is a class of climbing curve in a roadbed which reverses turn direction (inflection) twice on either side of a single tight curve that varies through an angle of about 180 degrees or more.
The Nilgiri Mountain Railway (NMR) is a 1,000 mmmetre gauge railway in Tamil Nadu, India, built by the British in 1908. The railway is operated by the Southern Railway and is the only rack railway in India.
A cable railway is a railway that uses a cable, rope or chain to haul trains. It is a specific type of cable transportation.
A bank engine, banking engine, helper engine or pusher engine is a railway locomotive that temporarily assists a train that requires additional power or traction to climb a gradient. Helpers/bankers are most commonly found in mountain divisions, where the ruling grade may demand the use of substantially greater motive power than that required for other grades within the division.
Combe Down Tunnel is on the now-closed Somerset and Dorset Joint Railway main line, between Midford and Bath Green Park railway station, below high ground and the southern suburbs of Bath, England, emerging below the southern slopes of Combe Down village.
The Ilfracombe branch of the London & South Western Railway (LSWR), ran between Barnstaple and Ilfracombe in North Devon. The branch opened as a single-track line in 1874, but was sufficiently popular that it needed to be upgraded to double-track in 1889.
The Ardglen Tunnel, also called the Liverpool Range tunnel, is a heritage-listed summit rail tunnel located on the Main North railway between Ardglen in the Liverpool Plains Shire and Murrurundi in the Upper Hunter Shire local government area, both in New South Wales, Australia. The tunnel crosses under the Liverpool Range near its east end, below Nowlands Gap, the crossing used by the New England Highway, and provides a vital link between Newcastle and Werris Creek. The tunnel was completed in 1877 and is owned by the Transport Asset Holding Entity, a state-owned corporation of the Government of New South Wales. It was added to the New South Wales State Heritage Register on 2 April 1999.
The South Devon Banks are a series of steep inclines on the ex-GWR railway line linking Exeter and Plymouth in Devon, England. These two cities are separated by the rocky uplands of Dartmoor forcing the early railway surveyors to propose that the line skirt the difficult terrain of the comparatively sparsely populated moorland. Isambard Kingdom Brunel, in surveying the South Devon Railway, opted to push a line along a coastal strip between the Exe and Teign valleys, and then to climb the southern outliers of Dartmoor making for the head of the Plym estuary. From Newton Abbot, the line climbs Dainton Bank, and from Totnes it climbs Rattery Bank, reaches a peak at Wrangaton summit, and then descends Hemerdon Bank to reach Plymouth. These three are collectively known as the South Devon Banks.
Crawford Hill is the name of a helper district with an average 1.55% eastbound grade between Crawford, Nebraska, USA, at an elevation of 3,678 feet (1,121 m), and Belmont, Nebraska at 4,499 feet (1,371 m) on the BNSF Railway Butte Subdivision. Crawford Hill is formed as it climbs the Pine Ridge escarpment, formations of buttes and grassy dense sand hills lined with ponderosa pines. Manned helper engines based in Crawford are used to help 18,000-ton loaded coal trains from Wyoming's Powder River Basin make it up the escarpment.
The Mount Tamalpais & Muir Woods Railway was a scenic tourist railway operating between Mill Valley and the east peak of Mount Tamalpais in Marin County, California, covering a distance of 8.19 miles (13.18 km), with a 2.88-mile (4.63 km) spur line to the Muir Woods. The railroad was incorporated in January 1896, and closed in the summer of 1930. Originally planned as a 4 ft 8 1⁄2 instandard gauge electric trolley line, the railroad was powered by a succession of geared steam locomotives. Billed as the "Crookedest Railroad in the World," the line was renowned for its steep and serpentine route, winding through picturesque terrain to a mountaintop tavern providing first-class hospitality and panoramic views of the San Francisco Bay Area. Despite its popularity, the railway met its demise following a fire in 1929, and dwindling ridership when the automobile could finally drive to Tamalpais' summit.
The Glenbrook deviation is a section of track on the Main Western line from Emu Plains to Blaxland stations in the Blue Mountains of New South Wales, Australia. The approximately seven-mile-long (eleven-kilometre) double-track deviation was constructed from 1911 to 1913 and replaced the single-track first Glenbrook deviation and the first Glenbrook Tunnel.