Recent developments in rollers include the provision for oscillation (for compaction
of thin layers and sensitive areas such as bridge decks) or vibration in both drums and sensors
for continuous monitoring of compaction of the mat. Another type of roller is one that consists
of three wheels of the same diameter and with equal compressive force per linear inch—all of
which are powered. Such rollers are suitable for compaction of thin lifts and city pavements built of
fragile structures where vibrations are not appropriate. Such rollers reduce shoving during compaction
and also provide the option of increasing the forces using water ballast. Finally, short radius
high vibration with smaller drums (e.g., 35.4 in., Sakai CR 270, http://www.sakaiamerica.com/
rollers_cr270_series.dws) are available for compaction around utilities as well as for compaction of
driveways, bike paths and road maintenance areas.