Safety Distance and Braking Distance in Sweden

Distance is the cheapest safety system in a car. It gives you time to see, decide and brake. The Swedish theory test checks two things here: that you know what the law requires, and that you understand how speed, road surface and reaction time change the distance you need to stop.

What the law requires

The Traffic Ordinance (Trafikförordningen 1998:1276) does not state a fixed distance in metres or seconds. It sets a standard you must meet:

3 kap. 2 §: the distance to the vehicle in front must be such that there is no risk of hitting it if it slows down or stops. The distance must also make it easier for other drivers to overtake you.
3 kap. 14 §: your speed must never be higher than allows you to keep control and stop within the part of the road you can see, and before any obstacle that can be foreseen.

So the question is never "how close is legal?" but "can I stop if the car in front brakes hard right now?"

One sign does set a fixed figure. C19, Minsta avstånd (Vägmärkesförordningen 2007:90) prohibits keeping a shorter distance to motor vehicles in front than the distance shown on the sign. Where it is posted, the figure on the sign is the legal minimum.

Stopping distance: reaction plus braking

Stopping distance has two parts:

Reaction distance: the distance the car travels from the moment you see the danger until your foot starts braking. During this time the car still moves at full speed.
Braking distance: the distance from when the brakes start working until the car stops.

Reaction distance grows in direct proportion to speed. At 90 km/h the car moves 25 metres every second, so even a one-second reaction costs 25 metres before braking has started. At 45 km/h, the same second costs half as much.

Braking distance grows much faster. Because the energy the brakes must remove depends on the square of the speed, doubling the speed roughly quadruples the braking distance on the same surface. Going from 50 to 100 km/h does not make braking twice as long. It makes it about four times as long.

The three-second habit

Because the law does not give a number, Swedish driving instruction commonly teaches a time gap of at least three seconds to the vehicle in front in good conditions. It is a habit, not a legal rule. To measure it:

Pick a fixed point, such as a sign or a lamp post.
When the car in front passes it, start counting: "one thousand and one, one thousand and two, one thousand and three".
If you pass the point before you finish, increase the distance.

A time gap works at every speed, because the distance grows automatically as you go faster. On wet or icy roads, with worn tyres, or behind a vehicle that blocks your view, three seconds is not enough.

What makes the distance longer

Several factors make the stopping distance longer:

Speed: the biggest single factor, because braking distance grows with the square of speed.
Road surface: wet roads, gravel, leaves, slush and ice give less grip. 3 kap. 15 § requires a sufficiently low speed on slippery roads.
Tyres: the legal minimum tread is 1.6 mm in summer conditions and 3 mm on winter tyres when the winter tyre rule applies (Transportstyrelsen). Worn tyres brake worse, especially on wet roads.
Load and downhill: 3 kap. 14 § lists the vehicle's condition and load among the things speed must be adapted to.
The driver: fatigue, alcohol, drugs and phone use all make reaction time longer. Under 3 kap. 1 §, you may not drive if illness, tiredness, alcohol or other substances mean you cannot drive safely.

Distance in other situations

Sideways when overtaking: you must leave a safe distance to the side of the vehicle you overtake (3 kap. 33 §).
Your own braking: do not brake suddenly or drive unreasonably slowly without a valid reason (3 kap. 16 §). When you intend to stop or slow down quickly, your brake lights must show it (3 kap. 65 §).
In queues: leave enough space that you can see the rear wheels of the car in front on the road. This gives room to steer around it if it stalls. This is a practical habit, not a legal rule.

Distance on the driving test

Trafikverket lists braking among the areas the examiner assesses, and the special manoeuvres part of the test can include braking exercises. During the drive, a gap that is too short is a typical sign of poor planning. Examiners look at whether you keep a distance that gives you time to act, not just whether you avoid a collision.

Typical theory test traps

"Double the speed, double the braking distance." No. Braking distance becomes roughly four times longer.
"The three-second rule is the law." The law requires a distance with no risk of collision. Three seconds is a teaching habit and may be too short in poor conditions.
Reaction distance on slippery roads. Ice makes braking distance longer, but reaction distance depends on speed and the driver, not on grip.
Forgetting the other purpose of distance. 3 kap. 2 § also asks you to keep a distance that makes it easier for others to overtake you.
Tired but sober. Fatigue is listed in the same paragraph as alcohol as a reason you may not drive.

FAQ

How many metres should I keep to the car in front in Sweden?

There is no general legal figure in metres. You must keep a distance that lets you stop if the car in front slows down or stops. Where sign C19 is posted, the distance on the sign is the legal minimum.

Why does braking distance grow so fast with speed?

The energy the brakes must turn into heat depends on the square of the speed. That is why doubling speed gives roughly four times the braking distance on the same surface.

Does a modern car with ABS stop in a much shorter distance?

ABS mainly helps you keep steering control while braking hard. It does not cancel the effect of speed, slippery surfaces or a slow reaction, so you still need the same margin.

Practise distance, reaction time and braking questions in Körkort Hero, available in 16 languages, until the "four times longer" rule feels automatic.

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