The Physics and Economics of Moving 44 Tonnes at 56mph
3 days ago
- #trucking
- #fuel-efficiency
- #logistics
- Trucks in the UK and EU are limited to 44 tonnes gross weight, with payloads around 28-29 tonnes.
- EU Directive 92/6/EEC mandates speed limiters at 56 mph (90 km/h) for trucks over 12 tonnes, causing slow overtakes due to minor speed variations.
- A 44-tonne truck at 56 mph has 25x the kinetic energy of a car, requiring longer stopping distances despite advanced braking systems.
- Fuel consumption for trucks is ~8.5 mpg (30 L/hour), costing ~£50,000 annually per truck, making small efficiency gains highly valuable.
- Diesel dominates freight due to its energy density (10 kWh/L), while batteries (0.25 kWh/kg) and hydrogen (1.3 kWh/L at 700 bar) face weight/volume trade-offs.
- Electric trucks suit urban/short-haul routes, while hydrogen may work for long-haul corridors, but infrastructure and efficiency challenges remain.
- Rail freight is efficient for bulk/long-distance but can't replace trucks for last-mile delivery due to flexibility and infrastructure mismatches.
- Truck idling (~1 L/hour) provides cab climate control, costing ~£1,000/year per truck, with battery APUs struggling to compete economically.
- Marginal improvements (aerodynamics, driver training, predictive cruise) compound savings, unlike 'snake oil' fuel additives promising unrealistic gains.