Safety distance in Spanish tunnels: 100 metres or 4 seconds
The exact rule for ordinary vehicles and vehicles over 3,500 kg when driving through a tunnel or underpass in Spain.
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Short answer
When you are not overtaking in a tunnel or underpass, keep at least 100 metres or 4 seconds behind the vehicle ahead. If your vehicle’s maximum authorised mass exceeds 3,500 kg, the minimum is 150 metres or 6 seconds.
The two thresholds
Article 95.6 of the General Traffic Regulation gives two equivalent ways to measure the required gap: distance in metres or time behind the preceding vehicle.
- Ordinary vehicles: at least 100 metres or 4 seconds.
- Vehicles with a maximum authorised mass over 3,500 kg: at least 150 metres or 6 seconds.
- The stated rule applies when the driver is not intending to overtake.
Why some online summaries get this wrong
A common error is to pair 100 metres with 6 seconds. That combines the ordinary-vehicle distance with the heavy-vehicle time interval. The current consolidated regulation pairs 100 metres with 4 seconds and 150 metres with 6 seconds.
Another unsafe shortcut is to treat the time interval as optional advice. The article presents metres and seconds as alternative legal minimums, not as a recommendation detached from the rule.
Other tunnel duties
The same provision requires drivers to use the appropriate lighting and rigorously follow tunnel rules, including restrictions on stopping, parking, reversing, changing direction, and overtaking. Always follow any stricter temporary signal or instruction.
Frequently asked questions
Is the tunnel gap 100 metres or 6 seconds?
No. For an ordinary vehicle it is at least 100 metres or 4 seconds. Six seconds belongs to the 150-metre rule for vehicles over 3,500 kg maximum authorised mass.
Does the 150-metre rule apply to every vehicle combination?
Article 95.6 states the higher threshold by maximum authorised mass: it applies when the vehicle exceeds 3,500 kg. Do not automatically apply it to every combination without checking that mass condition.
Do I need dipped headlights in a tunnel?
Drivers must use the lighting required for tunnels and underpasses. Follow the applicable tunnel signs and the General Traffic Regulation’s lighting rules.
Primary sources
Sources checked by Beep source-check workflow. We update rule-based pages when the underlying authority changes.
- General Traffic RegulationBoletín Oficial del Estado · Article 95.6 — tunnels and underpasses · retrieved 2026-07-12
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