A 32-year-old woman presents with sudden onset pleuritic chest pain and mild dyspnoea. She is on the combined oral contraceptive pill and recently completed a 6-hour car journey. Vital signs: BP 120/78 mm Hg, HR 95/min, RR 18/min, SpO2 98% on room air. Her Wells score for pulmonary embolism is low, and she meets all PERC (Pulmonary Embolism Rule-out Criteria). What is the most appropriate next step?