Background Speeding involvement has been reported to be as high as nearly 80% of all traffic crashes on national highways in Thailand. It was found that young drivers tend to drive faster and have higher risk of road crashes than other age group of drivers. Thus, it is necessary to understand the reason of speeding in the group of young drivers by examining their intention to speed and their driving behaviours.

Objectives This paper attempts to understand young drivers' speeding behaviour by using the Theory of Planned behaviour (TPB) and additional variables that are related to speeding behaviour, in the context of Thailand.

Methods Self-report survey was conducted on 800 college student drivers who intend to drive exceeding the speed limit, and tend to have higher record for speeding-related accidents.

Results/Outcome The results show that young drivers' speeding behaviour appears to be affected by perceived behavioural control, past behaviour, personal norms, intention to speed, affective and evaluative attitude towards compliance with speed limit, and social support. Furthermore, the effect of socio-economic characteristics and the vehicle usage such as gender, age, income level, university type, and location of university etc were significant factors to report that young drivers are more likely to be speeding offenders. Interestingly, racing movies and racing also make important predictors to influence drivers to drive exceeding the speed limit.

Significance/Contribution to the Field The results of this study can be used to suggest the need for implementing more effective countermeasure to control speeding behaviour of young drivers.