It is very important to know the tunnels safety distance in order to avoid potential accidents. The Highway Code sets a different distance for tunnels, and awareness of this is essential to ensure safety at the wheel. You should keep in mind that changes of light can be abrupt when entering and exiting the tunnel, as you pass from a lit area to darker area, making it even more necessary to keep your distance from other vehicles.
The safety distance in the M-30 tunnels is regulated by Article 95 of the Highway Code.
In general, if you do not plan to overtake the vehicle in front, you must always maintain a distance of at least 100 metres or a time interval of four seconds. In this way, if the vehicle ahead should brake or perform any unexpected manoeuvre, you will have enough time to react and avoid an accident.
If your vehicle has a Maximum Authorised Mass of over 3,500 kilos, you must maintain an increased safety distance from the vehicle in front of at least 150 metres, or a minimum time interval of six seconds.
It is important that you are aware that you may be fined by the authorities if they consider that you, as a driver, are not maintaining the safety distance in tunnels as established by the regulations. Obviously, these rules do not apply for either drivers of cars or drivers of vehicles of a Maximum Authorised Mass of over 3,500 kilos in the case of very congested traffic.
Many drivers use the ‘two-second rule’ to check if their safety distance is adequate, however, two seconds is not long enough. You have to follow the four-second rule, which can be applied simply by looking at a fixed object on the road, located in line with the vehicle in front of you, and saying: “1101, 1102, 1103 and 1104”. If you take at least that time to reach your chosen reference point, you will know that you have left enough time to react to any unanticipated event.
It should be remembered that, whilst they may sometimes contradict each other, signs always prevail over regulations. The minimum distance sign (R-300) indicates the minimum distance to be left between vehicles, except for when overtaking. The silhouettes are sometimes accompanied by a certain distance, such as 70 metres or 100 metres.