Weight limits, speed limits, fuel consumption at scale, and why trucks do the things that annoy you on the motorway.
You’re on the M1, doing 65, and two trucks pull out alongside each other. For the next several minutes you watch them drift past each other at what appears to be exactly the same speed. Your blood pressure rises. The inside lane backs up. Eventually the overtaking truck completes its pass, pulls in, and the world moves on.
Every driver in the UK has experienced this. Most assume the truck driver is being inconsiderate. The actual explanation involves EU legislation from 1992, engine ECU calibration tolerances, and the economics of a 10-hour driving day. Once you understand those, the rest of the commercial freight world starts to make sense, and you start to see why most “obvious” solutions to truck emissions hit hard physical constraints that aren’t going away.
This post is the foundation. Everything else on this blog (fuel additives, hydrogen, driver telemetry, emissions accounting) assumes you have this mental model.
The numbers, side by side
Most people’s intuitions about trucks are calibrated against cars. That calibration is off by about an order of magnitude in every dimension that matters.
Family car 44t Artic Gross weight 1,500 kg 44,000 kg 29× heavier Motorway speed limit 70 mph 56 mph EU limiter (90 km/h) Fuel consumption (cruise) ~45 mpg ~8.5 mpg 5× more per mile Fuel burn rate at cruise ~7 L/hr ~30 L/hr ~4× the flow rate Stopping distance (from limit) ~73 m ~150+ m Incl. thinking time Annual fuel consumption ~1,300 L ~43,000 L 33× more Annual fuel cost ~£1,500 ~£50,000 Annual CO₂ ~3.4 t ~113 t But carries 29t of freight Car: typical mid-size hatchback, 12,000 mi/yr. Truck: 6-axle artic, 80,000 mi/yr. Diesel at £1.15/L (ex-VAT bulk fleet price). CO₂ at 2.64 kg/L.
A fully loaded articulated truck weighs about the same as 29 family cars. It burns roughly 30 litres of diesel per hour at cruise. A fleet of 30 trucks will spend over £1.5 million on fuel this year. These numbers are the reason the industry is obsessed with marginal efficiency gains, and the reason it’s such a rich target for people selling snake oil.
What 44 tonnes actually means
The maximum gross vehicle weight for a standard six-axle articulated truck in the UK and EU is 44 tonnes. That’s 44,000 kg, set by law.
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