The term “steam roller” or “steamroller” is often used colloquially to refer to any sort of road rolling device, regardless as to how it is powered. Road rollers are heavy construction equipment used to smooth surfaces such as airstrips and roads. Today, it is quite rare to see a true steam roller powered with a steam engine, with most using internal combustion engines which run on fuels such as gasoline. Some construction and industry museums have examples of antique steam rollers on display, along with examples of even older roller designs, for those who are interested.
The earliest road rollers were drawn by horses or pushed by hand. They shared design commonalities with modern road rollers, consisting of a very heavy drum which was rolled over the surface to be compacted and smoothed. However, the weight was limited by the strength of the people or animals pushing or pulling the device, and when the steam engine was introduced, people were quick to adapt it to make the steam roller.
Steam rollers consisted of two very heavy drums, with the drums counterweighting each other so that the roadbed did not become ripply, as would happen with a single drum. The steam roller could be used to prepare roads and other flat surfaces at various stages of construction, and to apply layers of finish such as asphalt. Through the mid 20th century, several nations continued to use the steam roller, until internal combustion engines grew robust enough to handle the work.
Technically, the correct term for the construction equipment used today is “road roller,” because the devices are not steam powered. However, the steam roller is an iconic piece of equipment, and thus people often use the term generically to refer to road rolling devices. This has led to some confusion, with some people thinking that road rollers use steam somehow in their operations since they are obviously not powered by steam.
Walk behind and drive versions of the road roller are available, with the heaviest road rollers being used for tasks like landfill compaction. Also known as a roller-compactor, a road roller can vibrate during operation to compact the ground even more, and some use water or other lubricants to prevent materials on the roadbed from sticking to them. The drums can also be filled with water to make them heavier, as it is the weight of the machine which makes it an effective leveler and compacter.