French road sign regulation decrees that the waiting time at traffic lights must not exceed 120 seconds for car drivers, cyclists and pedestrians. Cities, which usually use traffic lights, have questioned this rule because they cannot comply with this requirement, especially on tramway crossings. The transport ministry has therefore opened discussions about modifying this rule and financed research work to assess the impact of waiting times on users' behaviour and safety. This paper presents the key facts and main results of this study. The behaviour of 44,000 drivers was observed in five cities. The rate of running red lights clearly depends on the length of waiting times. The 120 seconds maximum could be extended for drivers on tramway crossings. 8,000 pedestrians were also observed. Even if the waiting time is short, 64% of the pedestrians do not respect the red light. If it is long (between 90 and 300 seconds), it rises to 80%. An acceptability and credibility threshold exists and is less than 90 seconds. The research suggests waiting time limits should not be extended for pedestrians.