Emergency services have been at the scene on the A658 at Follifoot after the collision was reported just after 3.10pm today.
A North Yorkshire Police spokesman said: "One man is believed to be seriously injured and he is being treated by paramedics.
"Police have put in place road closures to divert traffic away from the collision scene.
"These are between the A658 and the A661 roundabout, at Buttersyke and also Rudding Lane.
"Motorists are urged to avoid the area until further notice."
In the meantime, witnesses to the collision are urged to call North Yorkshire Police on 101, select option one, and speak to the Force Control Room. Quote reference NYP-02122018-0325.