LK DMT Heavy Vehicle Written common mistakes
LK DMT Heavy Vehicle Written · Understand the traps and how to avoid them.
Treating the posted speed limit as a target and not slowing further for rain, night, narrow roads, or a loaded vehicle, so answers pick the limit figure when the safe speed is lower.
Candidates memorise the number on the sign and forget that the limit is a maximum for ideal conditions, not a recommended speed.
What to do instead
For every speed question, first ask what the conditions are (weather, visibility, load, road width) and choose the speed that lets you stop within the distance you can see to be clear; practise explaining aloud why the limit is not automatically correct.
Misreading regulatory signs by shape and colour, e.g. treating a circular red-bordered sign as a warning, or a triangular sign as a prohibition.
Learners study sign meanings as a list of pictures without learning the shape/colour system that lets you classify an unfamiliar sign.
What to do instead
Learn the four families first (circles = orders/prohibitions, triangles = warnings, rectangles = information/direction, octagon = stop) and sort flashcards by shape before memorising individual signs.
Ignoring lane markings and traffic-light phases in combination, e.g. proceeding on a green light without checking that the lane ahead is clear or that a filter arrow applies only to a turning lane.
Signals are learned in isolation, so candidates answer the light colour and overlook the arrow, stop line, or box junction that changes what is permitted.
What to do instead
When reviewing any junction question, name every control present (light, arrow, stop line, marking, sign) before deciding; practise describing a junction aloud in that order.
Braking late and relying on service brakes for long descents instead of selecting a lower gear and using engine braking, leading to overheated, fading brakes.
Candidates transfer car habits to heavy vehicles and underestimate how quickly a laden vehicle's brakes overheat on a gradient.
What to do instead
Adopt the rule: gear down before the descent, hold a steady low gear, use brakes in short controlled applications, and never coast in neutral; rehearse this on a known hill and state the gear choice in written answers.
Underestimating stopping distance and following distance for a heavy, loaded vehicle, especially when the load raises the centre of gravity or the total weight.
Candidates quote car stopping distances and do not scale them for mass, load, and road surface.
What to do instead
Work through stopping-distance calculations for a laden vehicle at several speeds and surfaces, and apply a minimum multi-second following gap that increases with load, rain, and speed.
Describing load restraint vaguely ('tie it down well') instead of specifying rated straps, correct attachment points, load distribution within axle limits, and checks after the first few kilometres.
Load security is studied as a concept rather than as a procedure, so answers lack the concrete steps examiners look for.
What to do instead
Memorise a load-security checklist (weight within limits and evenly spread, low centre of gravity, rated restraints in good condition, gates/latches secured, re-check after initial travel) and answer with those specific items.
Skipping or superficially performing the daily walk-around check, missing tyre damage, air leaks, lights, fluid levels, or insecure body parts, and driving a vehicle with a known defect.
Time pressure and routine familiarity cause drivers to glance rather than inspect, and candidates do not know which defects make a vehicle unroadworthy.
What to do instead
Learn a fixed inspection sequence (tyres and wheels, lights, brakes and air pressure, fluids, body and load, mirrors and wipers) and the rule that safety-critical defects mean the vehicle must not be driven until rectified.
Failing to recognise and act on warning signs of fatigue and impairment, or planning to 'push through' a long shift, and not knowing the licence, hours, and fitness obligations.
Candidates treat fatigue as a personal weakness rather than a hazard with legal and safety consequences, and they under-learn licensing conditions.
What to do instead
Study the licence classes, endorsements, medical and fitness requirements, and rest-break rules as concrete facts, and learn the early fatigue indicators with the required response: stop, rest, do not continue.
In hazard-perception scenarios, fixating on the most obvious hazard and missing the developing one (a pedestrian behind a parked vehicle, a cyclist in a blind spot, a vehicle emerging from a side road).
Attention locks onto the first thing seen, and candidates do not scan systematically or think about what could happen next.
What to do instead
Practise a scanning routine (far ahead, mirrors, near field, side roads) and for each scene ask 'what is the second and third hazard, and what is my escape route?' before answering.
Giving first-aid and emergency answers that are unsafe or incomplete, e.g. moving an injured casualty unnecessarily, forgetting to secure the scene and call emergency services, or omitting spill and fire precautions after a heavy-vehicle incident.
First aid is often skimmed, and candidates do not connect it to the specific risks of a large vehicle incident such as fuel spills, unstable loads, and blocked lanes.
What to do instead
Learn a fixed incident sequence (make the scene safe, warn other traffic, call emergency services with location and casualty details, then give care within your training) and state it in that order, including spill containment and fire risk.