Tier 1: Are there any high risk factors that mandate radiography? (Age > 65 years old, Dangerous MOI, or paresthesia in the extremities?) If Yes, refer them out for imaging. If No, proceed to Tier 2.
Tier 2: Are there low-risk factors that allows for safe assessment of ROM? (Simple rear end collision, sitting position in ED, ambulatory, delayed onset of neck pain, absence of midline cervical tenderness). If these aren't present and you can't assess ROM safely, refer them out for the imaging. If these factors are present, move on to tier 3 and test their ROM.
Tier 3: Do they have at least 45° of cervical spine active ROM rotation in both directions? If yes, no xray is needed. If not, refer them out.