A series of road accidents across Sydney and NSW have left a cyclist and a driver in critical condition and a pregnant woman taken to hospital.

A van and a taxi carrying the pregnant woman collided on William Street, near Sydney's CBD, about 6am (AEDT) on Thursday, police say.

The impact sent the taxi into a traffic light pole with such force that one of its wheels snapped loose and struck a third vehicle.

The taxi's occupants were trapped for some time before the woman was rushed to Royal Prince Alfred Hospital because of complications to her pregnancy and the driver for a broken leg.

In a separate incident, a man in his 50s was riding a bicycle along the Hume Highway, at Albury, when he was struck by a car about 9am (AEST) on Thursday.

An ambulance spokeswoman said the man suffered critical head injuries and was rushed to Albury Base Hospital.

He is expected to be airlifted to a larger hospital in NSW or Victoria.

In a third incident on Thursday, a man and a woman, also aged in their 50s, suffered head injuries after their mini-van and a truck collided on the Newell Highway, near Jerilderie in southern NSW, about 9.45am (AEDT).

The female driver suffered critical head injuries and was taken to Jerilderie Hospital initially.

Plans were being made to airlift her to a Melbourne hospital.

Her male passenger suffered a number of injuries and remains in a serious condition at Jerilderie.

The truck driver was taken to Finley Hospital and treated for shock.