The Idling Queue and the School Gate
You drive a diesel van for a small delivery firm. Each school morning you wait about 15 minutes outside a school gate with the engine idling so the cab stays warm and the battery keeps a phone charger and cooler running. The van is old, the exhaust smokes visibly when cold, and the queue of cars behind you also idles. Fuel records show consumption has risen about 12% over three months on the same routes. Tyres are at the low end of the recommended range, one is noticeably soft, and a roof rack left fitted carries nothing. The firm wants to cut fuel costs and has asked drivers for practical changes that do not delay deliveries.
1. Quantify the main avoidable fuel losses in this routine and rank them.
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The largest avoidable loss is the 15-minute idle every school morning. An idling engine returns zero kilometres per litre, and a cold diesel idling also burns extra fuel to keep itself warm while producing visible smoke. Over a working month that is several hours of pure consumption, and it is entirely avoidable by switching off.
The second is the soft tyre. An under-inflated tyre increases rolling resistance across every kilometre driven, not just the school stop, so it costs fuel continuously and also wears faster and heats up. The third is the empty roof rack, which adds aerodynamic drag at speed on every route. The fourth, less easy to quantify, is the cold-engine smoking, which suggests the engine is running rich and may need servicing. Ranked by litres saved per effort: idle elimination first, tyre pressure second, roof rack third, servicing fourth.
2. Propose a set of changes that cut fuel without delaying any delivery, and explain why each works.
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Switch the engine off during the school-gate wait and restart only when the queue moves; modern starters are designed for this, and the heater will stay warm for several minutes. Keep the phone charger and cooler on a separate battery pack rather than idling for them. Check and correct tyre pressures weekly when cold, aiming for the manufacturer's figure rather than the low end of the range. Remove the roof rack when it is not carrying anything, since drag rises with speed. Plan routes to avoid repeated stop-start congestion and combine drops where possible. Drive smoothly - early gear changes, steady speed, anticipation instead of late braking - because every hard acceleration burns fuel that braking then wastes. Keep windows closed at higher speeds and use ventilation rather than open windows. Finally, book the van for a service to address the cold-start smoking, since a poorly running engine wastes fuel regardless of driving style. None of these changes the delivery schedule.
3. How would you measure whether the changes worked, and what would you check if fuel use did not fall?
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I would measure over a fixed period using litres per 100 km and total litres per route, not just total spend, since fuel price moves. I would record the school-gate idle minutes per day, weekly cold tyre pressures, and whether the roof rack was fitted. Comparing the same routes before and after isolates the effect of the changes from seasonal or traffic variation.
If consumption did not fall, I would check: whether idle time actually dropped or was just moved elsewhere; whether tyre pressures were maintained or drifted back down; whether the roof rack was refitted; whether the service addressed the smoking; and whether driving style changed or drivers reverted under time pressure. I would also check for mechanical causes - dragging brakes, a clogged air filter, a failing thermostat keeping the engine cold - because these can swamp the savings from good habits and need fixing before the numbers will improve.