Detectives are appealing for women to come forward if they have been victims of a bus flasher.
It is believed a single offender may have been responsible for dozens of offences of indecent exposure on buses across Herts going back over months.
In one incident at 7pm on September 17 in Hemel Hempstead a woman on the 550 bus between Apsley and Bennetts End was left shaken after a man exposed himself to her and committed an indecent act.
Other offences have taken place on routes cross the county including St Albans, Stevenage, and Potters Bar.
The incidents have taken place at various times between midday and early evening.
In each case women have been targeted, leaving them shocked and upset.
In a statement Herts Police said: “Officers are appealing for witnesses and information in relation to a series of sex exposures that have taken place on buses in the county in recent months.
“Detectives are investigating a number of incidents that have occurred on buses in St Albans, Hemel Hempstead, Stevenage, Potters Bar, London Colney and Hatfield.
“If anyone believes they have any information about any similar incidents in the last four months, they are asked to contact Det Con Neil Barella on the Herts Police non-emergency number 101.”
Jobless Ben Harris, 28, from Hatfield Road in St Albans, has been charged with seven offences of sexual exposure.
He appeared before Hatfield Remand Court on October 18 and has been remanded in custody.