The hydraulic road roller is a machine that is powered by the use of hydraulic oil to create pressure. This pressure is then used to push down on the pavement and compact it, which makes it stronger. In contrast, the pneumatic road roller uses air pressure to push down on the pavement and compact it. The main difference between a pneumatic and hydraulic road roller is that one uses air pressure and one uses hydraulic oil to create pressure in order to push down on the pavement.