Background: Maintaining good quality CPR while transporting out-of-hospital cardiac arrest patients is very challenging. We aim to determine how different ambulance speed can affect the quality of chest compression performed either manually or mechanically. Methods: This was an observational manikin-based study. A total of 96 participants as well as two types of mechanical compression devices: Lucas-2 and AutoPulse, performed one minute of continuous chest compression on BT-CPEA programmed manikin while the ambulance travelled at different speeds, i.e., idle state, 30km/hr and 60km/hr. Seven outcome variables of chest compression were measured. Performance data of different groups of compressor were compared and analysed using repeated measures analysis of variance (ANOVA). Results: In manual chest compression, significant variation were noted among different speeds in term of average compression rate (p<0.001), average compression depth (p=0.007), fraction of adequate/insufficient compression depth and fraction of normal hands positioning with p=0.018, 0.022 and 0.034 respectively. Overall, AutoPulse and Lucas-2 were not affected by ambulance speed. Lucas2 showed more consistent average compression rate, higher fraction of adequate compression depth and reduced fraction of insufficient compression depth as compared to manual compression with p<0.001, 0.001 and 0.043 respectively. Conclusion: In this study we found that ambulance speed significantly affected certain aspects of manual chest compression most notably compression depth, rate and hand positioning. AutoPulse and Lucas-2 can improve these aspects by providing more consistent compression rate, depth and fraction of adequate compression depth during transport.