Spitting at Amersterdam's drivers and inspectors on the increase.
Security workers on Amsterdam's trams and buses have been issued with special kits to collect DNA from anti-social passengers who spit at staff.
Containers and gauze swabs have been given to security guards trained by forensic specialists to collect saliva samples.
These will then be given to prosecutors for further investigation before being sent to the Dutch National Forensic Institute where they will be held for 12 years.
The experimental policy comes in response to a recent spate of spitting attacks against drivers and conductors on Amsterdam's public transport network.
The city's transport company GVB says it hopes the new approach will eradicate the crime, which carries a three-month jail term or €4,000 fine.