It is a tourist railway that travels for 4.7 miles (7.6 km) from Llanberis to the summit of Snowdon, the highest peak in Wales.

[5] The SMR is the only public rack-and-pinion railway in the United Kingdom,[6] and after more than 100 years of operation it remains a popular tourist attraction, carrying more than 140,000 passengers annually.

However, in 1893 the Rhyd Ddu terminus of the North Wales Narrow Gauge Railways was renamed Snowdon, attracting many of the tourists who previously visited Llanberis and affecting the livelihoods of the accommodation providers who were Assheton-Smith tenants.

[10] After much persuasion, Assheton-Smith ultimately gave his assent to the construction of a railway to the summit,[3] and though still the principal landowner in the area, he was not a major influence in the company.

However, no Act of Parliament was now required, as the line was built entirely on private land obtained by the company, without any need for the power of compulsory purchase.

All tracklaying had to start from one end of the line, to ensure the rack was correctly aligned; so although the first locomotives were delivered in July 1895 very little track was laid until August, when the two large viaducts between Llanberis and Waterfall were completed.

In anticipation of this, Colonel Sir Francis Marindin from the Board of Trade was asked by Fox to make an unofficial inspection of the line on Friday 27 March.

On the upper section, the descending train hit a boulder that had fallen from the side of a cutting and several wheels were derailed.

An inquiry concluded that the accident had been triggered by post-construction settlement,[15] compounded by excess speed due to the weight of the train.

A man named William Morris Griffiths who had climbed Snowdon to see the sunrise, placed a stone on the rail and sitting on it, slid down the track at speed.

The Western Mail for 12 May 1943 reported that two trains per day would operate from Llanberis (at 1.15pm and 4.00pm) and people could still book to stay at the summit hotel.

[23] The new building, Hafod Eryri (loosely translated from Welsh as "high summer residence of Snowdonia"),[24] was officially opened by First Minister Rhodri Morgan on 12 June 2009.

This means that, if required, the line could be easily be converted to double track without the need to cut into the rock face to widen the formation.

Trains terminate at Rocky Valley Halt when the weather is too bad to allow them to proceed safely to the summit.

[26] For steam-hauled trains, the Llanberis shunt movement includes a trip to the water crane and coaling stage outside the locomotive shed.

It is stated by the management that the vast majority of passengers do not care whether the trains are powered by steam or diesel locomotives.

These pinions provide all the traction and braking effort, and the vehicle's wheels are free to revolve on the drive axles and serve only for support and guidance.

The requirement for the locomotives to have a hot fire burning efficiently for a solid hour has led to problems when best Welsh steam coal has not been readily available.

Between 1986 and 1992, four diesel locomotives were bought from the Hunslet Engine Company of Leeds, to a design and specification jointly developed with the railway.

[29] Named after Laura Alice's daughter, who cut the first sod in December 1894 in place of her mother, who was ill at the time.

Ran nameless until 21 June 1996 when it was named 'George' after George Thomas, 1st Viscount Tonypandy Withdrawn from use 2003, taken away for scrap July 2010 The boilers are inclined on the locomotives, to ensure that the boiler tubes and the firebox remain submerged when on the gradient, a standard practice on mountain railways – the locomotive always runs chimney-first up the mountain.

One result of the boiler's angle is that the Firehole door is at waist height, requiring the fireman to lift the coal some distance.

The boilers of these engines are fitted with superheaters, making them more efficient, and in place of a lever-type regulator they have a wheel that must be turned 2+1⁄4 times between closed and fully open.

For added safety with only one man in the cab, a dead-man device is included, a pedal that when released triggers the braking system to bring the train safely to a halt.

The generators had a Cummins engine rated at 137 kW (184 hp) which was run at a constant 1800 rpm and produced 440 V AC at 60 Hz.

The intention was that the diesel generator on the new locomotives would be switched off on the downhill runs, with regenerative service braking used to recharge the battery to provide power for the next ascent.

The railway now operates two services, depending on the motive power: Garmendale Engineering Ltd[36] was commissioned to build four brand new coaches for the 2013 season which are used exclusively with the diesel locomotives.

None of the contemporary reports on the railway refer to liveries but in coloured picture postcards and lantern slides the locomotives appear to be black.

All went well on the ascent, except that mist and cloud was covering the top of the mountain and extending down to about the level of Clogwyn Station.

About one-half mile (0.8 km) above Clogwyn, where the line runs on a shelf formed across a steep drop, the locomotive jumped off the rack rail, losing all braking force and accelerating down the track.