Road rollers use their weight to compress down the surface of the asphalt. The process of compression down can be either static or dynamic. In static compression, the machine is only rolled over the road surface,while in the case of dynamic compression mechanical means like vibration are used. As explained earlier, the road roller is made of two or more heavy drums.One of the drums is functioning as the drive while the other functioning as the pushing force. There are some special rollers, in which drum axles move in relative motion concerning each other. This allows them to adjust against the surface irregularities.