A woman is in a critical condition in hospital after a serious collision on the A505 Baldock bypass.
The incident happened at around 10.50pm on Friday on the northeast bound carriageway, close to the junction with Deadmans Hill.
A black Ford Focus was travelling towards Royston from Baldock in lane two, when it collided with a white Mercedes E220, which appears to have been driving the wrong way up the same carriageway.
The female passenger of the Mercedes - a 56-year-old woman from Graveley - is currently in a critical condition in hospital. The driver, a 64-year-old man from Letchworth, suffered minor injuries.
The driver of the Focus, a 20-year-old man from Royston, suffered leg injuries and was taken to hospital.
Detective Sergeant Shona Birkby, from the Serious Collision Investigation Unit, said: "We are appealing for witnesses who saw the collision, or anyone who saw the Mercedes prior to it, to please contact us. If you were driving in the area with a dash cam, we would also like to hear from you."
You can report information online at orlo.uk/9KGXw, speak to an operator in the Force Communications Room via the online web chat at orlo.uk/EOpbb or call the non-emergency number 101, quoting reference number 817 of 13 September.
If you have dash cam footage in relation to the collision, you can upload this at orlo.uk/ipqKt.
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