5.1 Hazard Perception & Following Distance
Key Takeaways
A hazard is anything — actual or potential — that may make you change speed or direction
Scan near, far, and mirrors continuously; a 12-second visual lead lets you plan instead of react
The two-second rule sets the minimum following gap in good, dry conditions
Double the gap to at least four seconds in rain or on slippery laterite roads
Leave extra space behind large vehicles, motorcycles, and whenever a tailgater is behind you
What Counts as a Hazard?
A hazard is anything — real or potential — that may cause you to change speed or change direction. Notice the word "may": a hazard does not have to be happening yet. A football rolling into the road is a hazard because a child may chase it. A tro-tro bus indicating and pulling to the kerb is a hazard because passengers may step out and other drivers may swerve around it. Parked cars, junctions, bends, animals near the roadside, a cyclist wobbling over a pothole — all of these are hazards even when everything looks calm.
Defensive driving means driving in a way that anticipates these hazards before they become emergencies. The defensive driver assumes other road users may make mistakes and keeps enough space and time to cope with those mistakes safely.
The Scanning Technique: Near – Far – Mirrors
Good hazard perception is not luck; it is a disciplined visual routine:
- Far ahead (12-second visual lead): Look as far down the road as you can see — about where you will be in 12 seconds at your current speed. This is where you spot junctions, queues, pedestrians gathering at crossings, and brake lights rippling back through traffic.
- Near and mid-distance: Check the space immediately around your vehicle for potholes, speed ramps, okada riders filtering through traffic, and children near the kerb.
- Mirrors: Glance at the interior and side mirrors every few seconds, and always before changing speed, changing lanes, or turning. You must know what is beside and behind you before you react to what is in front.
The cycle repeats continuously: far, near, mirrors, far, near, mirrors. When you spot a hazard far ahead, you can plan — ease off the accelerator early, cover the brake, adjust your position — instead of stamping on the brakes at the last moment.
Anticipating Vulnerable Road Users in Ghana
Certain road users need special anticipation because they can behave unpredictably and have little protection:
- Pedestrians: Especially near markets, lorry stations, and bus stops. Expect people to cross without looking, including between parked vehicles.
- Children near schools: Slow down well before school zones (where 30 km/h applies). A child may run into the road without warning.
- Cyclists and motorcyclists (okada): They can swerve suddenly to avoid potholes or puddles, may filter between lanes in traffic, and are hard to see at night. Give them generous room when passing.
- Tro-tro buses and shared taxis: They stop suddenly and often without clear signalling to pick up or drop passengers. Never follow them closely, and expect passengers to step out into the road.
- Animals in rural areas: Goats, sheep, and cattle wander onto unfenced rural roads, particularly at dawn and dusk. Reduce speed where animals are grazing near the road.
The defensive mindset is: what would I do if the worst happened right now? If the answer is "I couldn't stop in time," you are driving too fast or too close.
The Two-Second Rule
In good, dry conditions with an alert driver, the minimum safe following distance is set by the two-second rule:
- Watch the vehicle ahead pass a fixed point — a signpost, a tree, a road marking.
- Say to yourself: "Only a fool breaks the two-second rule." (This phrase takes about two seconds to say at normal speed.)
- If you reach the same fixed point before you finish the phrase, you are too close — drop back and repeat.
The beauty of the rule is that it self-adjusts with speed: the same two seconds produces a bigger gap at 90 km/h than at 50 km/h, exactly matching your longer stopping distance.
Adjusting the Gap
| Situation | Minimum gap |
|---|---|
| Good, dry conditions, alert driver | 2 seconds |
| Rain or wet road surface | 4 seconds (double) |
| Harmattan dust, fog, or poor visibility | 4+ seconds |
| Following a large truck or bus | 4+ seconds (you cannot see past it) |
| Following a motorcycle | 3–4 seconds (a rider can brake or swerve suddenly) |
| Being tailgated | Increase the gap ahead of you |
Large vehicles block your view of hazards ahead and may hide pedestrians stepping out — drop back so you can see around them. Motorcycles can slow or swerve suddenly for potholes and debris, so leave extra room in case the rider stops sharply. And if a driver is tailgating you, do not brake-check or speed up: increase your own gap to the vehicle in front so that you can brake gently and gradually, protecting yourself from being hit from behind, and let the tailgater pass when it is safe.
Space is the defensive driver's currency. You cannot control other road users, but you can always control the gap you keep.
You are following a large truck on a national highway and realise you cannot see either of the truck's side mirrors. What does this tell you, and what should you do?
The truck is overloaded; overtake it as quickly as possible
The truck driver probably cannot see you in the mirrors; drop back to a larger gap so you can see and be seen
You are at the correct distance; maintain your position directly behind the truck
The mirrors are only for reversing; ignore them and flash your headlights
On a dry, well-lit road in light traffic, which method correctly checks whether your following distance is safe?
Keep at least one car length behind for every 10 km/h of speed
Stay close enough that the vehicle ahead fills less than half your windscreen
Watch the vehicle ahead pass a fixed point and confirm you reach it no sooner than two seconds later
Match the speed of the vehicle behind you so traffic flows smoothly
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