Numbers & Distances
Braking-distance formulas, following distance, and every exact metre figure the exam expects you to know.
Reaction & braking distance formulas
| Quantity | Formula | At 100 km/h |
|---|---|---|
| Reaction distance (1 second) | speed ÷ 10 × 3 | 30 m |
| Braking distance | (speed ÷ 10)² | 100 m |
| Overall stopping distance | reaction + braking | 130 m |
At 30 km/h braking distance ≈ 9 m. Double the speed to 60 km/h and it becomes 36 m — 4×, not 2×, because the formula squares the speed.
General speed limits (car)
| Situation | Speed |
|---|---|
| Inside a built-up area | 50 km/h |
| Outside a built-up area (car ≤3.5t, no trailer) | 100 km/h |
| Autobahn / motorway-like separated road — cars & motorcycles | 130 km/h (advisory, not a hard limit) |
| Car + trailer, outside a built-up area and on the autobahn | 80 km/h |
| Car + trailer with a certified "100 km/h" trailer approval, on autobahns/motorway-like roads only | 100 km/h |
| Minimum speed to enter an autobahn at all | above 60 km/h |
The trap worth knowing: without a trailer, motorway vs. open road makes a real difference (130 advisory vs. 100 hard limit). With a trailer, that difference disappears — 80 km/h applies outside built-up areas and on the autobahn alike, unless your specific trailer carries the special 100 km/h homologation sticker.
130 km/h on the autobahn is a recommended speed (Richtgeschwindigkeit), not a legal maximum — but driving faster still increases fuel use sharply (up to 35% more at 160 km/h vs. 130 km/h) and accident severity.
Following (safety) distance
Rule of thumb: keep at least half your speedometer reading in metres. At 100 km/h, that's ≥ 50 m.
On a wide road with clear oncoming visibility, you must be able to stop within the distance you can actually see ahead.
What lengthens braking distance
- Wet or slippery road surface
- Driving downhill / steep gradient
- Towing a trailer with no brakes, or extra load
Metre distances — parking & stopping bans
| Situation | Clearance |
|---|---|
| Pedestrian crossing (before it) | 5 m |
| Junction (no cycle path) | 5 m |
| St. Andrew's Cross — built-up area | 5 m |
| St. Andrew's Cross — outside built-up area | 50 m |
| Junction with a cycle path alongside | 8 m |
| Sign your car could obscure (diagonal cross, Stop–Give Way) | 10 m |
| Bus / tram stop sign | 15 m |
| Narrow / hard-to-see stretch | no stop if < 3 m clear width |
Also banned, no fixed figure: level crossings, blind bends, hilltops, fire-access roads, taxi ranks, merging lanes, lowered kerbstones.
3-minute rule: under 3 min and you stay with the car = stopping. Over 3 min, or you leave the car = parking. Waiting at a closed level-crossing barrier is never "parking," however long it takes.
Vehicle length & other figures
| Situation | Figure |
|---|---|
| Length that triggers extra following distance (outside built-up areas) | > 7 m |
| Max car+trailer combination, unloaded | 18 m |
| Max car+trailer combination, loaded | 20.75 m |
| Heavy vehicles (>7.5t) waiting at closed barrier, outside town | 80 m marker |
Class B licence: tow up to 750 kg freely, or heavier if total combination mass stays under 3,500 kg.
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