A single axle tractor is a towing vehicle that features one rear axle rather than two, which is common on most larger towing vehicles. While most double axle or tandem axle tractors are used for hauling extremely large loads, a single axle tractor is more likely to tow only a small or medium-size load as compared to its larger counterparts. These tractors tend to get better gas mileage than larger, tandem axle trailers, though they cannot produce as much towing power. Depending on the towing configuration, the single axle vehicle may also be more maneuverable.
The rear axles on a tractor are usually drive axles, which means torque is produced at those axles and transferred to the road through the wheels and tires. A single axle tractor, therefore, will usually not produce as much torque as a tandem axle vehicle, making it suitable for lighter application duties. Many small to medium size box trucks, which feature fixed boxes mounted to the frame for enclosing goods being shipped, will feature only one rear drive axle because two axles will not be needed for the amount of goods being hauled. Trucks designed for towing heavier loads will feature two drive axles.
Large trailers can also be towed by a single axle tractor. This is usually done with smaller or lighter trailers, and like tandem axle tractor trailer combinations, the single axle tractor trailer combination is likely to be articulated; this means the trailer is attached to the tractor in such a way that the two units can pivot independently from each other. Articulation allows for better steering capabilities, since the combined unit is likely to be quite long; the vehicle would otherwise not be maneuverable at all around corners or turns. Having only one drive axle improves the tractor's handling in turns, and it also improves the vehicle's traction.
Like its larger counterpart, the single axle tractor may or may not feature a sleeper cabin, though it is less likely than a tandem axle tractor to feature one. A sleeper cabin is an extension behind the driving cabin in which a bed, chair, and even a table may be mounted so the driver can sleep and otherwise live out of the truck. This is usually reserved for long-haul truckers who will do multi-day trips across a region, and in most cases, a tandem axle tractor will be used for such purposes. It is not unheard of, however, for a single axle tractor to be used for such purposes.