Multiple reports of high-speed racing and antisocial behaviour have forced harbour officials to ban overnight parking on the East Arm.
Officials say the restrictions are temporary and have been enforced for islanders' safety.
More than a hundred 10-hour parking spaces are unavailable between 9pm and 6am.
Harbourmaster Captain David Barker says that the pier will close at times when parking is not usually required.
"There have been several occasions at night were bikes and cars have been racing up and down the East Arm, endangering themselves and potentially anybody who happens to be there."
The parking area was returned to public use in February, after being used as a Covid testing facility during the pandemic, and the authorities say the speeding and anti-social drivers appeared soon after.
Guernsey students heading to university to receive Meningitis B vaccine
Guernsey teen set for month-long marathon swim
Guernsey Post introduce new services from early July
Guernsey Waste improves the quality of its free garden compost
Guernsey cat lover to ride the length of Britain in nine days
Unclaimed CI Co-op cash funds community projects
Work to commence on 70 affordable flats and homes in Guernsey
A new tax, more 'proportionate' to wealth, to be put to Guernsey's States
