Around one million people are killed world wide every year in road-traffic accidents. The risks and consequences of accidents increase progressively with speed, which ultimately is determined by the individual driver. The behaviour of the motorist thus affects both her own and other peoples safety. Internalisation of external costs of road transport has hitherto been focused on distance-based taxes or insurance premiums. While these means, as they are designed today, may affect driven distance, they have no influence on driving behaviour. This paper argues that by linking on-board positioning systems to insurance premiums it is possible to reward careful driving and get drivers to self select into different risk categories depending on their compliance to speed limits. We report two economic field experiments that have tested ways to induce car-owners to have technical platforms installed in their vehicle in order to affect the extent of speeding. It is demonstrated that a bonus to remunerate those that have the device installed, tantamount to a lower insurance premium, increases drivers?propensity to accept the technical devices. In a second experiment the size of the bonus is made dependent on the actual frequency of speeding. We find that this is a second way to discipline users to drive at legal speeds.