Capped Ambition: What a 60mph Van Policy Actually Returns on Forty Vans

The proposal arrives in the same form every time. Someone in finance has read that aerodynamic drag rises with the square of speed, someone else recalls a trial at a previous employer, and by Friday there is a paper recommending a 60mph ceiling across the van fleet. The benefit is expressed as a percentage. The cost is expressed as nothing at all. Neither figure survives contact with a fuel-card statement.

This is an attempt to price both sides, using the fill data and telematics most UK operators already hold, and to set out a trial design that does not turn a fuel decision into a driver-relations problem.

The policy only touches one road type

Begin with the law, because it materially shrinks the prize. A goods vehicle not exceeding 3.5 tonnes is already restricted to 50mph on a single carriageway and 60mph on a dual carriageway in England and Wales. The motorway limit of 70mph is the only place a 60mph policy genuinely bites.

For a fleet of urban and suburban vans, that is fatal to the business case. If 80 per cent of your mileage is A-road and town work, the policy governs a rounding error. The honest first step is to run a route-mix report from telematics and rank the fleet by motorway mileage. In a typical forty-van operation we would expect twelve to sixteen units to account for the overwhelming majority of motorway miles. The policy should be aimed at those units, not the whole fleet.

Calibration before commitment

Most speed-cap calculations fail at the point of measurement. A UK speedometer may over-read by up to 10 per cent plus 6.25mph, and many do. A driver reporting that he "sat at 70" may have been travelling at 63mph. GPS-derived telematics speed is the only defensible reference, and the sampling interval matters: a 60-second poll will miss the bursts that dominate consumption.

Two further controls are needed before any comparison. First, separate indicated speed from true speed for at least a fortnight of baseline running. Second, use brim-to-brim litres at the same pump rather than fuel-card spend, because price varies by site and will otherwise contaminate the result.

The per-van arithmetic

Take a representative 3.5-tonne panel van: 22,000 miles a year, of which 9,900 are motorway. Baseline motorway consumption at a true 70mph is 30.0mpg for a laden van of this type; at a true 60mph, telematics-matched fill data from comparable fleets typically shows something between 32.5 and 34.5mpg, heavily dependent on gradients, payload and wind. We have used 33.6mpg, a 12 per cent improvement, which is optimistic-but-achievable rather than best-case.

Per van, the saving is 161 litres a year — roughly two tankfuls — worth about £238, or £19.83 a month. Across forty vans held to the policy the gross figure is £9,520 a year, and that assumes every one of them spends 45 per cent of its mileage on a motorway, which they will not.

The hour you have to pay for

The same 9,900 motorway miles take 23.6 hours longer at 60mph than at 70mph. Divide the annual saving by that figure and the break-even value of a lost hour is £10.08.

That is the whole argument in one number. A fully loaded driving hour in the UK — wage, employer's National Insurance, pension, holiday cover — sits comfortably above that. If the cap pushes work into overtime, agency cover or a paid sixth shift, the policy is cash-negative before it is a mile-per-gallon success. If the schedule has slack and drivers are salaried, the time cost is real but not yet cash, and the saving stands.

The sensitivity is worth stating plainly. At £1.35 a litre the break-even hour falls to £9.21; at £1.65 it rises to £11.26. Diesel price moves the case, but not decisively. Schedule slack moves it decisively.

Why the first five miles per hour matter more

Drag rises with the square of speed, so the marginal saving per mph is larger at the top of the range. Dropping from 70 to 65mph recovers slightly more than dropping from 65 to 60mph, while costing roughly half the elapsed time. Operators wanting most of the benefit with least of the friction should model 65mph as a serious alternative rather than treating 60 as the only respectable number.

Running the trial in one depot

Choose a depot with the highest motorway mileage, not the most compliant manager. Take a two-week baseline in the same season as the trial; December and January data is contaminated by idling, weather and Christmas volumes. Then run eight weeks of advisory capping — telematics alerts and weekly driver scorecards, no limiter — against an unchanged control depot.

Communicate the measure before the measure is enforced. Drivers accept a stated number far more readily than a discovered one, and the framing matters: litres saved, not speed reduced. Publish depot-level results, never individual league tables, at least until the numbers are stable.

Finally, hold back on a hard limiter. A governed 60mph removes driver discretion entirely, including on the day a vehicle is running late with a timed delivery. Advisory first, limiter only if the advisory phase holds up.

Four numbers that end the trial early

Stop the policy, or narrow it, if any of the following appears: measured motorway improvement below 6 per cent; overtime or agency claims exceeding the fuel saving in any four-week period; a rise in missed delivery windows; or driver turnover at the trial depot diverging from the control. Any one of these is sufficient. Fuel policy is a cost measure, not a moral one.

What we would do

The defensible version is narrower than the memo. Cap the fourteen or so vans that genuinely run long motorway miles, set the ceiling at 65mph rather than 60, run it as advice for two months, and reconcile the litres before anyone signs a limiter order. The dividend exists. It is smaller than the percentage suggests, it belongs to a minority of the fleet, and it is only collected if the schedule can absorb the extra twenty minutes a week.