A 86-year-old woman has been taken to Prince Charles Hospital in Merthyr Tydfil after being struck by a HGV lorry.
Gwent Police is appealing for information about the accident which happened on A472 Nelson Road in Ystrad Mynach.
The collision was reported at 1.50pm today.
The woman is said to be in a stable condition.
A temporary road closure is in place on the Nelson Road from Ystrad Mynach, by the junction of the Castle View Estate, up to the Railway Bridge and will remain closed for the next couple of hours.
Anyone with information about the collision is asked to contact Gwent Police on 01633 838111 or the Collision Investigation Unit on 01633 642404.
On Monday, maintenance work started on the retaining walls along the road. It is not yet known if the HGV involved in the collision was connected with the works.