As shown in illustration No. 2 in my previous article, there are two main types of humps. As regards the engineering features of the grades no two yards are alike, and therefore no hard and fast rule can be laid down as to the most effective grade. Each yard must be built according to the types of wagons, weather conditions (including temperature and prevailing winds), general lay-out of points and crossings, and the distance wagons have to run to clearance points after leaving the hump.

In the colder climates such as are met with in America, either two humps are provided or the hump has a jacking device which provides a steeper grade when necessary.

With the English type of wagon it is generally recognised that the grade should be such that the speed of a wagon, after leaving the top of the hump does not exceed 10 to 12 miles per hour. With the introduction of mechanical track brakes this speed can be increased with safety, as any undue speed can be checked by these brakes.

The hump yard is, in effect, a flat yard with an artificial hump on the shunting leg so arranged that shunting engines instead of “setting back” at speed, stopping suddenly, and then pulling ahead again, merely push the wagons over the hump at a steady speed of about two miles per hour. As soon as the detached wagons arrive at the top of the hump they fall away from the train. Providing the grade is correctly set and the speed of the train is suitably adjusted, a train of 70 wagons or so can be passed over the hump and the wagons marshalled into their respective roads without the engine coming to rest.

It can be seen that the advantages of using an artificial hump in place of a flat shunting neck are considerable. Firstly the average time to make one cut or shunt in a modern hump yard with mechanical points operation is approximately 22 seconds, that is to say, a 70 wagon train with 50 cuts can be split up in 18 to 20 minutes. Contrast this with, at the very least, one hour for the same work with flat shunting. I have in mind a yard where, with the construction of a hump, the same traffic is handled with a reduction of 13 engine hours each day. In New Zealand this would represent a saving of over £2,000 per annum. I can imagine some of my shunter readers wishing they had a few humps in some of our shunting yards on a busy night.

Secondly, there is a considerable reduction in the cost of operating the locomotive as the work performed is much less, and the wear and tear on the brakes and draw gear is reduced to a minimum.

Thirdly, as explained in regard to “all gravity” yards, the damage to rolling stock and freight by constant jerking is eliminated.

Fourthly, the shunting staff can be greatly reduced; in fact, with electrical points operation and mechanical track brakes, the work of the ground staff on the hump is confined solely to receiving incoming trains preparatory to passing them over the hump, the actual movement on the hump being controlled by one signalman and the track brake operators located in towers at convenient points.

This refers to the most modern yard. The usual. method is for brakemen to be stationed in the yard to steady the wagons as they run down from the hump. In America as many as 40 men are required at one time for this service, and a special track is provided to bring them back to the hump on motor jiggers. As previously explained, this is due to the brakes being on the top of wagons, necessitating men riding with each cut.

Taking everything into consideration it can be seen that hump shunting offers very considerable advantages over flat shunting in large yards. The hump method is, however, only considered economical when handling 500 or more wagons per day.