The Roads and Maritime Service is investigating a section of the Great Western Highway at Linden following the second serious accident involving a cyclist in two years.
Both accidents were caused by tree branches hanging over the eastbound breakdown lane.
A 48-year-old man was rushed to Westmead Hospital with a fractured skull and punctured lung last Wednesday after losing control of his bicycle about 6.55am.
Police said the man, who was wearing a helmet, took evasive action to avoid a fallen tree limb.
It was an almost identical scenario to a crash that saw Leura man Ross Pointer taken to hospital with multiple skull fractures in September 2012.
Mr Pointer, 37, witnessed the aftermath of the Linden accident last week while driving on the highway.
"I felt almost like a ghost watching the same thing that happened to me," he told the Gazette.
He planned to contact the RMS about safety at that section of the highway.
"It was a tree branch overhanging the road [that caused my accident]. I caught my handlebar on it and went straight over," he said.
A spokeswoman for the RMS said "inspections of the Great Western Highway at Linden are carried out every two days to ensure roadside vegetation is maintained in line with national guidelines".
"Additional inspections are carried out after severe weather and immediately if issues are raised by the community," she said.
"Roads and Maritime inspected this section of the highway immediately after the crash occurred and investigations are continuing.
"Roads and Maritime will continue to work with Blue Mountains Council and cycling groups."