Between 1919 and 1925, the South African Railways (SAR) placed five Class NG G11 Garratt locomotives with a 2-6-0+0-6-2 Double Mogul type wheel arrangement in service on the Avontuur narrow gauge line through the Langkloof, and also in Natal.

[1][2][3][4] The challenges of Africa resulted in the regular need for double-heading of steam locomotives on heavy trains.

[4] On the South African Railways (SAR) narrow gauge lines, that solution was found in 1914 when orders were placed with Beyer, Peacock & Company for a narrow-gauge Garratt locomotive.

Alternative solutions would either be double-heading longer trains or re-building and re-aligning large parts of the lines to accommodate heavier locomotives.

To accommodate the pivoting, the steam and exhaust pipes have flexible connections between the engine units and the central cradle.

The use of a Garratt locomotive enables the capacity of a line to be approximately doubled without having to strengthen the track, bridges and culverts, or re-align the curvature.

[6] Probably the greatest advantage of the Garratt was that, with its boiler and grate area suspended between two engine units without the need to leave room for coupled wheels and cylinders, wide and deep fireboxes with large grate areas and large diameter boilers were possible.

With each set of cylinders and coupled wheels constituting a separate engine, the result was two locomotives in one, with one huge shared boiler which needed only one crew.

A Garratt is therefore a single locomotive with double the tractive effort and, with its weight distributed over a long and flexible multi-axle wheelbase, a lower axle loading.

[3] Although they had already been ordered in 1914, production was disrupted by World War I. Beyer, Peacock & Company was only able to deliver the first three locomotives in 1919 after cessation of hostilities.

[1][2] After completion of the Otavi Railway's gauge widening by April 1961, a flood of Class NG15 locomotives from South West Africa swamped the Humewood Road depot in Port Elizabeth.

In Port Elizabeth, they were employed on shed and yard duty and on transfer trips to and from the docks until, after the arrival of the Class 91-000 diesel-electric locomotives in 1973, they were withdrawn from service in October 1974.

NG54 was restored in Bloemfontein in 1989, After a period working the Apple Express out of Port Elizabeth, it ended up staged out of service at Humewood Road until it was removed by Sandstone Estates in 2011 for safe-keeping.

NG55 was restored to full working order also at Bloemfontein for the Patons Country Narrow Gauge Railway (PCNGR) at Ixopo in Natal by 2005.