A man was flown to hospital with life-threatening injuries following a road traffic collision on Friday.
The incident occured in Jupiter Drive, near the junction with Solway, at around 5.30pm.
A black Pulse moped was being ridden along the road when, for reasons unknown at this stage, it was in collision with a white Seat Ibiza.
The moped rider, a man aged in his 40s, was flown to Addenbrooke’s Hospital where he remains in a critical condition.
The driver of the Seat, a woman in her 20s, was uninjured.
Herts Police are appealing for anyone who saw the incident, or events leading up to it, to get in touch.
Call PC Jackie Lister in the Forensic Collision Investigation Unit on 101, quoting ISR 524 of January 15.