Grove Road is closed both ways near Portland Prison while a crane is being operated between Shepherds Croft and Incline Road.
The diversion is not thought suitable for larger vehicles.
The road is due to re-open at 6pm.
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Police are trying to locate missing man, David Saunders. He has short white hair and a white beard.
It's dull and wet again out there this morning but it may just get a bit brighter later on this afternoon.
Cloudy and rainy to kick off this morning but it should dry out for some brighter breaks this afternoon.