The Caterpillar D9 is a large track-type tractor

Tractor

A tractor is a vehicle specifically designed to deliver a high tractive effort at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or construction...

 designed and manufactured by Caterpillar Inc.

Caterpillar Inc.

Caterpillar Inc. , also known as "CAT", designs, manufactures, markets and sells machinery and engines and sells financial products and insurance to customers via a worldwide dealer network. Caterpillar is the world's largest manufacturer of construction and mining equipment, diesel and natural gas...

 Though it comes in many configurations it is usually sold as a bulldozer

Bulldozer

A bulldozer is a crawler equipped with a substantial metal plate used to push large quantities of soil, sand, rubble, etc., during construction work and typically equipped at the rear with a claw-like device to loosen densely-compacted materials.Bulldozers can be found on a wide range of sites,...

 equipped with a detachable large blade and a rear ripper attachment.

The D9, with 354 kW (474 hp) of gross power and an operating weight of 49 tons, is in the upper end (but not the heaviest), of Caterpillar's track-type tractors, which range in size from the D3 57 kW (77 hp), 8 tons, to the D11

Caterpillar D11

The Caterpillar D11 is a large bulldozer, manufactured by Caterpillar Inc. in East Peoria, Illinois, and mainly used in the mining industry. Primarily designed as a bulldozer, it also used for push-loading scrapers, and ripping rock overburden.-D11N:...

 698 kW (935 hp), 104 tons

Tonne

The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

.

The size, durability, reliability, and low operating costs have made the D9 one of the most popular large track-type tractors in the world.