The theoretical part of the skid control (risk avoidance) training for category B students at the initial stage. The theory prepares students for the exercises on the skid training ground.
1. Purpose and structure of the training
The aim is for the student to understand why accidents happen on slippery roads and to be able to anticipate and avoid danger, not just recover from a skid.
Learning outcomes. By the end of the training the student:
- explains how speed, road surface and tyres affect grip and stopping distance;
- recognises signs of slippery conditions and adjusts speed and following distance;
- knows how ABS, ESC and traction control work and what they cannot do;
- knows what to do in emergency braking, when avoiding an obstacle and when the car skids;
- understands that the best technique is not getting into the situation at all.
2. Grip and speed
A car touches the road through four tyre contact patches, each roughly the size of a palm. Everything the car does — accelerating, braking, turning — goes through these patches.
Grip is limited. It depends on the road surface, the tyres and the vehicle load. If the forces needed for braking, accelerating and turning together exceed the available grip, the wheel starts to slide.
Friction circle (Kamm circle): a tyre can deliver either braking force or cornering force, but not both at full strength at once. Under hard braking little grip is left for turning, and vice versa. That is why on slippery roads you brake before the bend, while driving straight.
Kinetic energy grows with the square of speed: E = m · v² / 2
- Twice the speed = four times the energy and roughly four times the braking distance.
- 60 km/h instead of 50 km/h means almost 45% more energy.
Weight transfer: when braking, weight shifts to the front axle (front wheels grip better, rear wheels worse); when accelerating, to the rear. That is why suddenly lifting off the throttle in a bend can make the rear slide.
3. Road surface and weather
At the same speed, grip on different surfaces can differ by up to 8 times. The friction coefficient (μ) shows how well the tyre grips the road.
| Surface | Friction coefficient μ (approx.) |
|---|---|
| Dry asphalt | 0.7–0.9 |
| Wet asphalt | 0.4–0.6 |
| Packed snow | 0.2–0.3 |
| Ice | 0.1–0.2 |
| Wet ice (around 0 °C) | 0.05–0.1 |
Warning signs and danger spots:
- Black ice — a thin transparent layer of ice; the road just looks wet. It forms around 0 °C, especially at night and early in the morning.
- Bridges, overpasses, forest sections, shaded spots — freeze earlier and thaw later.
- First rain after a dry spell — dust, rubber and oil residue turn into a slippery film.
- Wet leaves, clay, sand and gravel on asphalt, road markings, manhole covers, tram rails.
- Before junctions and stops — snow is polished into ice by braking.
- Ruts — climbing over the edge of a rut can suddenly pull the car sideways.
Aquaplaning: if the tyre cannot clear water from the contact patch, a layer of water forms under it and the car loses steering control. The risk grows with speed, water depth and tread wear. Sign: the steering goes light, engine revs rise. What to do: ease off the throttle, keep the wheel straight, do not brake hard, wait for grip to return.
4. Stopping distance
On ice at 90 km/h the stopping distance is over 340 m — more than five times longer than on dry asphalt.
Stopping distance = reaction distance + braking distance.
- Reaction distance — the distance the car travels from noticing the danger to starting to brake. Reaction time is usually ~1 s; with fatigue, a phone or alcohol it is much longer. The road surface does not affect it.
- Braking distance depends on the square of speed and on grip: s = v² / (2 · μ · g), where v is speed in m/s (km/h ÷ 3.6), μ the friction coefficient and g = 9.81 m/s².
Example calculation (reaction time 1 s, reaction + braking distance):
| Surface (μ) | 50 km/h | 90 km/h |
|---|---|---|
| Dry asphalt (0.8) | 14 + 12 = 26 m | 25 + 40 = 65 m |
| Wet asphalt (0.5) | 14 + 20 = 34 m | 25 + 64 = 89 m |
| Snow (0.25) | 14 + 39 = 53 m | 25 + 127 = 152 m |
| Ice (0.1) | 14 + 98 = 112 m | 25 + 319 = 344 m |
- Reducing speed is the most effective way to shorten the stopping distance.
- On slippery roads increase the following distance several times: at least 2–3 s on dry roads, 6 s or more on snow and ice.
- Where you would have stopped on a dry road (from 50 km/h), on ice you will still be moving at over 40 km/h.
5. Tyres and driver assistance systems
Assistance systems help you use the available grip better, but they do not increase it: no system changes the laws of physics.
Tyres
- Winter tyres are mandatory from 1 December to 1 March; studded tyres are allowed from 15 October to 31 March (the Transport Administration may change the period depending on the weather).
- Minimum tread depth: 3 mm for winter tyres, 1.6 mm for summer tyres.
- Correct tyre pressure (see the manufacturer’s label on the door pillar or in the owner’s manual); check it when the tyres are cold.
- All four tyres should be the same (type, tread pattern, wear).
| System | What it does | What the driver must know |
|---|---|---|
| ABS (anti-lock braking) | Prevents the wheels from locking under braking, so the car stays steerable | Press the brake hard to the floor and hold it; pedal vibration and noise are normal. On loose snow and gravel the braking distance may even get longer. |
| ESC / ESP (stability control) | Brakes individual wheels and reduces engine power when the car starts to slide sideways | A flashing warning light = you are at the limit of grip, slow down. |
| TCS / ASR (traction control) | Stops the driven wheels from spinning when accelerating | When pulling away in deep snow it may need to be switched off temporarily. |
| Brake assist (BAS) | Detects emergency braking and applies full braking force | Works only if the driver presses the pedal quickly and decisively. |
Danger: assistance systems can create a false sense of security. The driver goes faster because the car “holds the road” — until the grip limit is exceeded and the system can no longer help.
6. What to do in a dangerous situation
Eyes and hands move together: look where you want to go, not at the obstacle.
Emergency braking with ABS
- Press the brake hard and fast to the floor (with a manual gearbox, the clutch too).
- Keep the pedal down until the car stops; do not release it because of the vibration.
- Look towards free space and, if needed, steer around the obstacle.
Emergency braking without ABS: brake so that the wheels do not lock; if they lock, release the pedal for a moment and brake again (cadence braking). A car with locked wheels does not respond to steering.
Avoiding an obstacle: if the stopping distance is not enough, it is often better to steer around. With ABS you can brake and steer at the same time. Steering inputs must be quick but not excessive; straighten the wheel immediately after passing.
| Situation | What happens | What to do |
|---|---|---|
| Understeer (front slides) | The car goes straight on in a bend, steering has no effect | Reduce speed (ease off, brake gently) and reduce the steering angle so the front wheels grip again |
| Oversteer (rear slides) | The rear swings out, the car starts to spin | Look where you want to go, steer into the skid (counter-steer), do not brake hard; once the car stabilises, straighten the wheel immediately |
| All wheels slide | The car keeps moving regardless of steering | Release the brake and the throttle so the wheels can roll and grip again; look towards free space |
On the training ground these situations are practised at low speed. In real traffic recovering from a skid is always uncertain — that is why learning to avoid skids matters more.
7. Risk perception and avoidance
Most accidents on slippery roads are caused not by a lack of skill, but by too high a speed and too short a following distance for the conditions.
- Overconfidence — new drivers often rate their abilities higher than they are; skid training does not make anyone an “ice expert”.
- Hurry and time pressure — in winter, plan extra time for the trip.
- Distraction — phones, passengers and music lengthen reaction time.
- Fatigue, alcohol, medication — slow down reactions and impair judgement.
Principles of risk avoidance
- Adapt your speed to the conditions — the speed limit applies in good conditions.
- Keep a sufficient following distance — at least 6 s on slippery roads; leave room at the sides too.
- Look far ahead — spotting danger early gives you time to react calmly, not abruptly.
- Drive smoothly — accelerate, brake and turn gently; brake before the bend, on the straight.
- Test the grip — in a safe place with no traffic behind, a light test brake shows how slippery the road is.
- Keep the car in good condition — tyres, brakes, clean windows, lights and mirrors.
- Consider whether the trip is necessary — in extreme conditions the best decision is to postpone it.
8. Practical part and safety on the training ground
- Braking on dry and slippery surfaces — comparing stopping distances.
- Emergency braking with ABS and avoiding an obstacle.
- Braking in a bend and choosing the right entry speed.
- Feeling understeer and oversteer and regaining control.
Safety rules: everyone wears a seat belt; no loose objects in the car; phone on silent; drive only on the instructor’s signal and at the speed given.
9. Summary
On a slippery road grip can be up to 8 times lower and the stopping distance several times longer. Assistance systems help but do not change physics. The techniques learned on the training ground are a last resort — the best protection is a speed suited to the conditions, a sufficient following distance and looking far ahead.