Rail workers want authorities to use “spit kits” to identify the saliva of unruly commuters.

The Rail Tram and Bus Union (RTBU) says the portable testing equipment could be used to drive down the increasing number of spitting assaults on Sydney station guards, staff and drivers.

Spit kits have been successful in the UK in allowing rail workers to gather a saliva specimen to be matched against existing DNA databases.

In the UK, for the 12 months from April 2012, 73 per cent of all spit kit submissions resulted in the identification of an offender, leading to the convictions of over 400 offenders.