12.2 Speed Limits & Stopping Distance

12.2 Speed Limits & Stopping Distance

Quick Answer: The maximum speed on all roads is 50 km/h unless speed limit signs show otherwise (including variable speed-limit signs). Never drive so fast that you cannot stop well within the distance you can see clear. Stopping distance = thinking distance + braking distance. Use at least a two-second gap in good conditions (more for heavy vehicles); in bad conditions use four seconds or more. On wet roads, allow braking distance at least doubled. Do not brake sharply except in an emergency.

Section 12.1 established fitness and attention. This section converts those ideas into how fast you may go and how much space you must leave. Part B of the Taxi Written Test uses three-option items in the same style as the private-car written test; the facts below are classic RUC Chapter 5 material (“How Fast,” “Stopping Distance,” following distance).

The Default Limit: 50 km/h Unless Signed Otherwise

Memorise the RUC headline speed rule:

The maximum speed on all roads is 50 km/h unless speed limit signs show otherwise.

Implications for study and practice:

1. 50 km/h is the default ceiling, not a target you must hit. Many urban taxi situations need much lower speeds for pedestrians, wet tram tracks, school zones, sharp bends, or dense traffic.
2. Where a higher or lower limit applies, signs (including gantry or roadside limit signs) tell you. Obey the signed limit for that stretch.
3. Variable speed limit signs exist on some roads. The displayed figure is the limit while it is shown — do not keep an old number in your head after the sign changes.
4. Ending a higher-limit stretch is marked so that drivers return to the appropriate lower limit (including return toward the general 50 km/h regime where that applies). Read the signs; do not assume expressway speeds continue into ordinary streets.

Legal limit vs safe speed

The exam loves the distinction:

Driving at exactly 50 km/h can still be too fast in fog, heavy rain, or a crowded market street. The RUC’s control idea is: never drive so fast that you cannot stop well within the distance you can see to be clear.

Adjust for Weather and Visibility

Slow down further when conditions reduce grip or sight:

• Wet roads — less tyre grip; longer braking distance
• Fog or mist — shorter clear sight distance; you must be able to stop inside what you can still see
• Heavy rain, spray, standing water — risk of reduced control; smooth inputs only
• Glare, night, or unlit stretches — sight distance shrinks; speed must shrink with it

If you cannot see far, you must go slower, not “keep the limit and hope.” Taxi passengers may complain about caution; the Written Test (and real liability) rewards the driver who protects the clear-stop rule.

Do Not Brake Sharply Except in an Emergency

Smooth driving is a safety skill:

• Harsh braking surprises following drivers and can cause rear-end collisions
• Passengers (especially elderly or standing-entry moments before seating) can be injured by sudden stops
• Sharp braking is a symptom that speed was too high or gap was too small for the hazard you eventually saw

RUC teaching: plan early, ease off the accelerator, brake progressively. Reserve sharp braking for true emergencies, not for routine junction arrivals you should have anticipated.

Stopping Distance = Thinking Distance + Braking Distance

Learn the equation as a fixed exam fact:

Stopping distance = thinking distance + braking distance

Thinking distance

Thinking distance is how far the vehicle travels from the moment a hazard appears to the moment you start effective braking. It grows when reactions are slow.

Factors that increase thinking distance:

• Slow reactions (including distraction)
• Tiredness
• Illness
• Lack of concentration
• Impairment from drink, drugs, or some medicines (links back to Section 12.1 fitness)

Braking distance

Braking distance is how far the vehicle travels while the brakes are applied until it stops. It grows when grip or braking efficiency falls.

Factors that increase braking distance:

• Wet or slippery roads
• Poor brakes
• Poor tyres (worn tread, under-inflation)
• Higher speed (energy rises steeply with speed — small speed increases create large extra braking distance)
• Heavier load (relevant when the taxi is full of passengers and luggage)

Combined teaching picture

If a Part B stem asks why stopping distance increased on a rainy night after a long shift, the full answer often includes both longer thinking (tired) and longer braking (wet).

Wet Roads: At Least Double Braking Allowance

Official RUC emphasis for wet conditions:

On wet roads, allow at least double the normal braking distance.

Practical translation for taxi work:

• Leave much larger following gaps in rain
• Arrive at junctions and crossings earlier with gentler deceleration
• Treat painted lines, metal surfaces, and polished bitumen as extra slippery when wet
• Do not assume ABS or modern tyres cancel the double-allowance teaching — the Code still requires the extra margin

Safe Gap and the Two-Second Rule

Ideally, the gap to the vehicle ahead should be at least enough for your full stopping distance if that vehicle slows or stops suddenly. In moving traffic, drivers use a practical time gap.

Good conditions: two-second rule

In good conditions, leave at least a two-second time gap to the vehicle in front. Heavy vehicles need more than two seconds because they take longer to stop.

Bad conditions: double or more

In bad conditions (wet, poor visibility, tiredness, heavy traffic turbulence), double the gap to four seconds or more.

How to measure two seconds (RUC method)

1. Pick a fixed mark ahead (lamp post, sign, road marking, bridge shadow).
2. When the vehicle in front passes that mark, start counting: “one thousand one, one thousand two.”
3. If you reach the mark before you finish the count, you are too close — drop back.
4. In rain or poor conditions, extend the count to four seconds (or more).

This method works at any speed because it is a time gap, not a fixed number of metres that fails when speed changes.

What the gap is for

• Time to see a brake light
• Time to decide and move your foot
• Distance to brake without hitting the vehicle ahead
• Buffer so you are not forced into panic (sharp) braking

If you often need panic action, the RUC diagnosis is blunt: you were too fast, too close, or both.

Speed Choice for Professional Taxi Drivers

Apply the rules as a hierarchy:

1. Obey the signed or default legal maximum (50 km/h unless signs say otherwise; variable signs when present).
2. Reduce below that maximum whenever clear sight distance, weather, traffic, road surface, or passenger safety requires it.
3. Maintain a two-second (or longer) gap; never “close up” to stop other drivers cutting in if that destroys your stopping room.
4. Brake early and smoothly so passengers are not thrown forward and following drivers are not surprised.
5. Ignore pressure from passengers who want illegal speed or tailgating — your licence and their lives are not negotiable for a few minutes saved.

Common Exam Traps

Memory Hooks

• 50 unless signs (including variable signs) say otherwise
• See clear → can stop inside it
• Stop = think + brake
• 2 seconds good weather; 4+ bad weather; more if heavy vehicle
• Wet → ≥ 2× braking allowance
• Smooth > sharp except true emergency

Closing Checklist for Section 12.2

1. Default maximum 50 km/h on all roads unless speed limit signs show otherwise; watch variable limits.
2. Never drive faster than you can stop within the clear distance ahead; slow for wet, fog, mist, and poor sight.
3. Stopping distance = thinking + braking; know what increases each part.
4. Ideal gap ≈ stopping distance; practical rule two seconds (more for heavy vehicles); bad conditions double or more.
5. Two-second method: mark + “one thousand one, one thousand two.”
6. Wet roads: braking allowance at least doubled.
7. No sharp braking except emergency; professional taxis choose smooth, legal, sight-limited speed.

Next, Section 12.3 applies speed and space rules to overtaking, white lines, bus and light-rail lanes, and lane discipline — where many Part B errors become collisions or fixed-penalty habits.