A man suffered serious injuries when he fell out of a moving taxi in Bath, police believe.
Officers said he had suffered a head injury and had been taken to the Royal United Hospital.
The A3062 North Road has been closed in both directions between the Combe Road junction and the North Road junction.
The taxi driver has been arrested following the incident at about 2245 GMT on Tuesday night.
An Avon and Somerset Constabulary spokesman said the man had later been transferred to Frenchay Hospital, near Bristol with a suspected fractured skull.
The road was cordoned off and a diversion put in place
Police are appealing for witnesses.