We tested the prototype willingness model (PWM). The participants (N = 198) completed online questionnaire measures of PWM constructs (Time 1) and subsequent speeding behaviour (Time 2). Path analyses showed that the PWM accounted for 89% of the variance in subsequent (self‐reported) speeding behaviour. This significantly exceeded the variance accounted for by the theory of planned behaviour. In line with the PWM, both behavioural intention and behavioural willingness had direct effects on behaviour. Behavioural willingness had a significantly larger effect. Attitude and subjective norm both had indirect effects on behaviour through both behavioural intention and behavioural willingness. Prototype (similarity) perceptions had indirect effects on behaviour through behavioural willingness only. The findings support the notion that driving is governed by reactive decision‐making (willingness), underpinned by prototype perceptions, attitudes and subjective norms, to a greater extent than it is deliberative decision‐making (intentions), underpinned by attitudes and subjective norms. The implications for safety interventions are discussed.