Explantion: You should always be prepared to react to hazards ahead. If the vehicle in front is moving from side to side, it may indicate that the driver is not paying full attention or that their driving is impaired by drink, drugs or tiredness. If you think the vehicle is a risk to the public safety, the matter should be reported to the Gardaí or to traffic watch (lo-call 1890 205 805), but not while driving.