Fine weather brought trail bike riders out in force on Saturday but led to police involvement too, with a number of complaints of disturbance in the Lerwick area.
A 17-year-old youth was seriously injured when he fell off a trail bike at Sands of Sound around 2pm on Saturday.
The youth, who was not wearing a helmet, was taken to the Gilbert Bain Hospital where his condition was said to be not life threatening. A hospital spokeswoman said on Monday he was doing well and would possibly be discharged later that day.
Police are warning that helmets should be worn at all times and if trail bikes are used on the road they must be legal.
In an unrelated incident police seized a dirt bike on Saturday night that was being driven on the road without insurance, road tax or MOT. The rider was cautioned and charged and will be reported to the procurator fiscal.
In addition to possible criminal proceedings, the rider will have to pay over £100 to get his bike back.
In the light of these incidents and the number of reports of disturbance, police say robust action will be taken against riders in an attempt to prevent breaches of the peace.