Extra safety measures are being introduced at the Port of Felixstowe following the death of a docker last week.
Dennis Burman, a 51-year-old trainee, fell more than 100 feet to his death from one of the cranes.
He died in Ipswich Hospital after the accident at the Trinity Terminal at the Suffolk container port.
Prohibition notices have been issued on five cranes by the Health and Safety Executive (HSE) after identifying the risks of operating the equipment.
The notices mean only one person other than a docker in the ground-level checker's cab will be allowed on a crane while is it operating.
Other people will be allowed on stationary cranes.
The port's corporate affairs manager Paul Davey said there are occasions when more than one person has to be up there.
"There is a need and there always will be a need to train people fully, there is a need for maintenance on cranes and work to go on on cranes and there will be occasions when more than one person needs to be on a crane."
An internal inquiry into Mr Burman's death is under way alongside an HSE investigation.