Environmental driving, fuel efficiency and noise
This domain tests whether you can link driving decisions to fuel, emissions and noise in a measurable way. Expect questions with figures: speed versus consumption, idling, AdBlue and the noise consequences of braking technique.
Where the fuel goes
For a bus with a trailer, air resistance dominates above about 60 km/h and rises with the square of speed. Going from 80 to 90 km/h costs roughly 20 % more fuel for the same distance; on a 400 km leg that is about 20 litres and around 50 kg of CO2.
Eco-driving that examiners can see
- Look far ahead and lift off early instead of braking late; every unnecessary brake application is fuel already burned.
- Accelerate firmly but briefly, change up around 1,200–1,500 rpm, and use the highest gear that pulls cleanly.
- Use cruise control on the flat, allow speed to build slightly downhill and bleed off uphill.
- Switch the engine off at terminals and long stops; idling burns about 1–2 litres an hour and is restricted by local rules at many Danish bus terminals.
- Keep tyre pressures at the manufacturer's figure for the axle load; soft tyres cost fuel and overheat.
- Plan route and load: an empty trailer still costs fuel and still counts against the length and weight limits.
Noise
- Retarders and engine braking are effective and generally quieter than hard service braking; use them in towns and at night, and respect local restrictions.
- Avoid unnecessary revving and horn use; close doors and compartment lids gently and do not run refrigeration units longer than needed.
- Report damaged silencers and rattling body panels - a loose trailer floor generates complaints.
Emissions hardware
AdBlue must be kept topped up; a bus that runs dry derates and cannot be driven normally. Defeating the SCR system is illegal and is checked at inspection and roadside control.
Worked example
Route A: 400 km at 80 km/h, consumption 25 L/100 km, so 100 litres. Route B: the same route at 90 km/h, 30 L/100 km, so 120 litres. The faster plan saves around 45 minutes but costs 20 litres - roughly 240 DKK at 12 DKK per litre - plus about 53 kg CO2 at 2.65 kg per litre of diesel. On a daily schedule the saving outweighs the time gained, and 80 km/h is the legal maximum for the combination anyway.
Traps
- Believing a light trailer costs nothing in fuel.
- Idling for ten minutes at a stop to keep the cabin cool.
- Ignoring a rising AdBlue warning until the vehicle derates.
- Assuming a retarder is always the quietest option without checking local rules.