Vehicle Weights, Dimensions & Stability

Why does a double-deck bus need to be driven especially carefully around bends and roundabouts?

• AIts high centre of gravity makes it more likely to tip if taken too fast✓
• BIts longer braking distance means it cannot slow down for bends at all
• CIts extra weight on the front axle makes the steering fail on tight bends
• DIts height means it always loses grip on any curve in wet weather

Answer: A tall vehicle such as a double-decker has a high centre of gravity, so cornering forces can cause it to roll or tip if you take a bend or roundabout too quickly. Reducing speed before the bend keeps it stable.

Before driving a coach on an unfamiliar route, why is it important to know the vehicle's height?

• ASo you can work out the correct tyre pressures for the journey
• BSo you can decide how many passengers the coach is allowed to carry
• CSo you can set the tachograph to the right mode for the trip
• DSo you can avoid low bridges and other height-restricted structures✓

Answer: Knowing your vehicle's travelling height lets you avoid low bridges and other restrictions and prevents bridge strikes, which is why the height should be displayed in the cab. Height does not determine tyre pressures, passenger capacity or tachograph mode.

A sign shows a maximum weight limit for a road ahead. How does it apply to your bus?

• AYou must not use that road if your vehicle's weight exceeds the limit shown✓
• BYou may use the road provided you drive slowly across any weak section
• CThe limit applies only to goods vehicles, so a passenger bus is exempt
• DYou may use the road if you have no passengers on board at the time

Answer: A weight-limit sign applies to the actual weight of your vehicle, and you must not enter if you exceed it, as the restriction often protects a weak bridge or structure. It is not waived by driving slowly or by carrying no passengers.

How does carrying a full load of passengers affect your bus compared with running empty?

• AIt has no measurable effect because passengers are a very light load
• BIt increases the weight, so braking distances and stability are affected✓
• CIt shortens braking distances because the extra weight adds more grip
• DIt only matters at motorway speeds, not on ordinary town-centre routes with frequent stops

Answer: A full load significantly increases the vehicle's weight, which lengthens braking distances and changes how the bus handles, so you allow for this. Passengers are far from negligible, and extra weight does not shorten stopping distances.

On a three-lane motorway, which lane must a bus or coach longer than 12 metres not use?

• AThe left-hand lane, which is kept clear for vehicles joining the motorway
• BThe middle lane, which is reserved for vehicles that are overtaking
• CThe right-hand lane, which such vehicles are not permitted to use✓
• DThe left and middle lanes, which are kept for cars and light vans

Answer: On a motorway with three or more lanes, a bus or coach over 12 metres long is not allowed to use the extreme right-hand lane except in special circumstances. It uses the left and middle lanes as appropriate.

What is the maximum length of a rigid bus with two axles in Great Britain?

• A18.75 metres
• B12 metres
• C13.5 metres✓
• D15 metres

Answer: DfT guidance gives 13.5 metres for a bus with two axles and 15 metres for a bus with more than two axles. 18.75 metres is the limit for an articulated bus.

What is the maximum length of a rigid bus with more than two axles?

• A15 metres✓
• B16.5 metres
• C13.5 metres
• D12 metres

Answer: A bus with more than two axles may be up to 15 metres long. The 16.5-metre figure applies to articulated goods vehicles and 12 metres to rigid goods vehicles.

What is the maximum length of an articulated (bendy) bus?

• A21 metres
• B18.75 metres✓
• C16.5 metres
• D15 metres

Answer: DfT's guidance on maximum vehicle lengths sets 18.75 metres for an articulated bus.

What is the normal maximum width of a bus or coach?

• A2.55 metres✓
• B2.50 metres
• C3.00 metres
• D2.75 metres

Answer: Buses and coaches are normally limited to 2.55 metres wide, not counting mirrors. You still need to allow for mirror width in narrow places.

You pull away from a bus stop on full lock. Why should you check your offside mirror?

• AThe rear overhang can swing out into the next lane✓
• BThe front wheels will run over the kerb on that side
• CThe mirror shows whether passengers have sat down
• DThe doors on that side may open while you turn

Answer: On a long vehicle the body behind the rear axle swings out in the opposite direction to the turn. Pulling out on full lock can bring the rear overhang into the path of passing traffic.

Where should heavy luggage be carried on a coach to keep it stable?

• ALow down, in the underfloor luggage lockers✓
• BIn the gangway, where the driver can see it
• CAt the very back, behind the last row of seats
• DOn the overhead racks above the passenger seats

Answer: Keeping heavy items low keeps the centre of gravity low, which improves stability. Heavy bags on overhead racks could also fall and injure passengers.

The underfloor lockers on your coach are packed with heavy luggage. What could this affect?

• AThe tachograph's record of driving
• BOnly the fuel economy of the coach
• CAxle weights, braking and steering✓
• DThe accuracy of the speedometer

Answer: Heavy luggage adds weight and can overload an individual axle, which affects braking, steering and tyre wear. Know your vehicle's plated weights.

You are turning left at a junction in a long bus. How can you stop the rear wheels mounting the kerb?

• ATurn in quickly so the rear wheels follow the front
• BGo further forward before you start to turn✓
• CBrake firmly while the steering is on full lock
• DTurn early, keeping the front close to the kerb

Answer: The rear wheels of a long vehicle cut in on a turn. Driving further forward before turning keeps the rear wheels clear of the kerb, while watching your nearside for cyclists.

On a route with trees beside the road, what should you watch for in a double-deck bus?

• ABranches that could strike the upper deck✓
• BTree roots that could damage the fuel tank
• CLeaves blocking the view of the speedometer
• DShadows that could affect the tachograph

Answer: Overhanging branches can strike the upper deck and break windows, injuring passengers. Keep well clear where branches hang low over the road.