The international consensus on the benefits of active fire protection in tunnels has changed from being against the idea to one of guarded support. The most influential international standards, PIARC and NFPA, now contain positive remarks about active fire protection systems, even if they stop short of recommending them in all new tunnels. It has been recognised that active fire protection systems can limit the size of a fire so that ventilation systems will be able to handle it and fire-fighters will be able to approach to complete extinguishment. In addition it is recognised that active fire protection systems will limit damage to the tunnel in the event of fire, so that even a fire involving several heavy goods vehicles will not close the tunnel for a lengthy period. While the consensus has moved, there is still much debate about when an active fire protection system is appropriate; to what extent it can be assumed to limit the maximum heat release rate; and to what extent it will limit the maximum tunnel lining temperatures and so reduce the specification for passive structural fire protection. Surprisingly, given that over 100 tunnels are now fitted with an active fire protection system, there is also debate over the initial installation costs and the running costs. As these issues are addressed, using data, a consensus will emerge. Meanwhile most European countries now routinely consider whether to fix an active fire protection system in new tunnels, and some are considering whether active fire protection systems can be used to upgrade fire safety in existing tunnels. Looking ahead, research projects are investigating to what extent an active fire protection system can limit the maximum heat release rate; whether an active fire protection system combined with longitudinal ventilation offers equal or better life safety than transverse ventilation; and how to specify design or performance test criteria for tunnel active fire protection systems.