The following imaging algorithm for adult head and neck injury (this algorithm also contains the algorithm for pediatric head and neck imaging) is from the National Institute of Health and Care Excellence (NICE). It is from Head injury: Triage, assessment, investigation and early management of head injury in children, young people and adults. NICE guidelines [CG176] Published date: January 2014
Please see also Introduction to the Guidelines for the Management of Acute Cervical Spine and Spinal Cord Injuries. [PubMed Citation] [Full Text HTML] [From the previous HTML link you can also download the PDF which is easier to review than the HTML version] Neurosurgery. 2013 Mar;72 Suppl 2:5-16. This citation has a brief readable summary of all the adult and pediatric recommendations.
And see The 2012 Guidelines for the Management of Acute Cervical Spine and Spinal Cord Injury. [PubMed Citation] Neurosurgery. 2013 Mar;72 Suppl 2:2-3.
And see Updated Guidelines for the Management of Acute Cervical Spine and Spinal Cord Injury. [PubMed Citation] Neurosurgery. 2013 Mar;72 Suppl 2:1.
The above are excellent British Guidelines but The American Guidelines (Introduction to the Guidelines above) would favor high quality CT (if available) over plain radiographs of the cervical spine.
Additional Resource:
Imaging Algorithm For Pediatric Head and Neck Injury From NICE. Posted on September 3, 2015 by Tom Wade MD