How to Choose the Right HGV PMI Inspection Interval

Is a six-week PMI a legal requirement?

No. There is no single statutory week-count that every goods vehicle must use. The common “six-weekly inspection” figure is industry practice for many operations, not a law that every fleet must copy.

The Guide to Maintaining Roadworthiness (opens in a new tab) expects safety inspections at the frequency the operator has arranged and notified. The goods vehicle operator licensing guide (opens in a new tab) expects those inspections, including brake tests, inside the ISO weeks you notified, with a planner set at least six months ahead.

What determines the inspection interval?

Set the interval from how the vehicle is used: annual mileage, type of work, roads, loading, age and condition, and how quickly defects appear. A tipper on rough sites usually needs a shorter gap than a lightly used trunking tractor on good roads.

The guide expects the interval to be justified by the operation and then kept. A long interval that looks convenient on a spreadsheet, with late sheets and rising defects, is not a justified arrangement. A short interval that nobody can staff is also a system failure.

4-, 6-, 8- and 10-week intervals

Operators commonly declare intervals in that range. None of those figures is “the legal one”. A four-week gap can be right for severe work. An eight- or ten-week gap can be right for lighter work when the history supports it and the sheets stay on time.

Do not treat a neighbour’s six-week programme as your legal duty. Treat your declared weeks, your planner and your completed sheets as the arrangement a traffic commissioner can test.

Can you change your PMI interval?

Yes, when the operation changes or the evidence says the current gap is wrong. Changing the inspection arrangements means updating the vehicle operator licensing service so the notified weeks match what you actually run.

A planner that silently shortens or lengthens the gap without updating the licensing service creates two stories: one on the licence file and one in the workshop. Investigations score that gap.

What evidence should support the decision?

Write why the interval fits the work: mileage bands, defect trends, prohibition history, age of the fleet, and trailer use. Keep that note with the maintenance system. When you lengthen an interval, show that defects and late inspections are under control first.

When you shorten it, say what triggered the change: rising defects, a prohibition, a new contract, or older vehicles. Evidence beats a verbal “we always do six weeks”.

What about trailers?

Trailers need their own safety-inspection programme. Interval choice follows the same logic: use, condition and notified arrangements. A tractor on eight weeks does not automatically put every trailer on eight weeks if the trailer work is harsher.

Third-party trailers still need roadworthiness control when you use them. The walkaround covers the day; the PMI programme covers the planned mechanical inspection for trailers you maintain.

Reviewing inspection effectiveness

An interval only works if sheets arrive on time, defects are assessed and repaired, and brake performance is measured. Late inspections at a “strict” six-week interval are worse evidence than an eight-week interval that is kept.

Use the monthly compliance checklist to sample whether dates match the declared weeks. Recurring defects between inspections can mean the gap is too long, or that repairs are not sticking.

Maintenance planner

Official guidance expects a maintenance planner looking at least six months ahead, with safety inspections and the annual test on it. The planner is how you prove the interval is real before the week arrives.

A wall chart, a spreadsheet or software can all be a planner. What matters is that the next dates follow the notified weeks and that completed sheets close those dates.

Example scenarios

Harsh tipper work

A small tipper fleet on construction sites declares a shorter interval because bodies, suspension and brakes take more punishment. The evidence is mileage, site conditions and defect history — not a preference for more paperwork.

Light trunking

A trunking tractor on good roads with stable defect rates may justify a longer declared gap. The sheets must still arrive inside those weeks, with laden brake tests as the guide requires.

Ageing assets

Older vehicles often need a tighter programme. That is operator judgement supported by condition and history. Software may warn on age; the licensing declaration is still the operator’s decision.

Declaring on VOL vs workshop practice

Legal requirement and official guidance: the interval you notify on the vehicle operator licensing service is the arrangement you are expected to keep. Operator procedure: how the workshop books bays, how contractors quote, and how planners print lists. Those two stories must match.

A common failure is declaring six weeks on the licensing service while the workshop runs “about every two months when the bay is free”. Another is declaring eight weeks while a contractor’s standing order still prints six-weekly sheets. Investigators read the notified weeks first, then ask whether the sheets land inside those ISO weeks.

When you change the interval, update the licensing service so the notified weeks match what you will run. Then change the planner and any standing workshop orders in the same change window. A verbal “we’ve gone to eight weeks” that never reaches the licensing file is not an updated arrangement.

Keep a short change log: date, old weeks, new weeks, reason, who authorised it, and confirmation that the licensing service was updated. That log sits with the maintenance system and answers the first question a traffic commissioner will ask when the planner and the licence file disagree.

Brake tests and the inspection interval

Official guidance in the Guide to Maintaining Roadworthiness (opens in a new tab) and the licensing guide expects brake performance to be assessed as part of the safety-inspection programme — not as an optional extra when the roller is free. The interval sets how often the full inspection (including brake assessment) should land; it does not replace the need for laden or suitably representative brake evidence where the guide expects it.

Operator procedure: decide how brake tests sit inside each PMI — same day, same visit, or a controlled follow-up that still closes the inspection. A PMI sheet marked complete with “brakes to follow” and no closed brake result is weak evidence that the inspection happened as notified.

Do not stretch the interval because brake capacity is scarce. If the roller or laden route is the bottleneck, fix capacity or shorten the programme you can actually complete — do not leave brake assessment as an orphan task that drifts past the ISO week. Late brake evidence after a “completed” PMI is a pattern investigations notice.

Multi-depot fleets and mixed intervals

One operator licence can support more than one justified interval. Tippers at Depot A on four weeks and trunking tractors at Depot B on eight weeks is fine when each class is justified, notified and kept. Mixing intervals without a clear asset-class rule is what creates chaos.

Operator procedure: group assets by use and condition, not by which planner opened last. Write which classes sit on which weeks. When a vehicle moves depot or duty, reassess the class — a tipper moved onto trunking may justify a longer gap; a trunking tractor put on aggregate work may need a shorter one. Update the licensing arrangement if the notified weeks for that vehicle change.

Multi-depot control fails when each site invents its own “local practice”. Central transport management should hold the declared weeks, the justification note and the forward planner. Depots execute the diary; they do not silently rewrite the interval because a contractor prefers a different standing order.

Seasonal work and contract changes

Operations change. Peak construction seasons, winter gritting, harvest contracts and short-term trunking deals can all change how hard vehicles work. Official guidance expects the inspection frequency to fit the operation you actually run — not the operation you ran last spring.

Operator procedure when work intensifies: review defect rates, prohibitions and late sheets before the peak. Shorten the interval if the evidence says the current gap is too long, update the licensing service, and replan the next six months. Do not wait until prohibitions arrive to discover the old gap was wrong.

When work lightens, do not automatically lengthen the interval on hope. Show that defects and lateness are under control, write the justification, update the declaration, then move the planner. A quiet month on the phone does not by itself justify a longer mechanical gap.

Contract wins that add mileage, sites or trailer types should trigger the same review as a seasonal peak. Put the review date in the monthly compliance loop so interval choice is a scheduled management act, not a hallway conversation after a failed MOT.

How a Traffic Commissioner investigation sees intervals

From a licence perspective, the story is simple: what did you notify, did you keep it, and can you show the system works? The goods vehicle operator licensing guide (opens in a new tab) frames maintenance arrangements as something you declare and operate. A traffic commissioner looking at maintenance will test that chain, not whether you copied a neighbour’s six-week habit.

Weak evidence looks like this: declared six weeks; planner shows eight; sheets land at ten; brake tests missing; defect rates rising; no written reason for the gap. Strong evidence looks like this: declared weeks match the planner; sheets close inside ISO weeks; brakes assessed; late inspections investigated; interval changes documented and re-notified.

Late inspections matter more than the marketing label on the interval. An eight-week programme kept on time with closed brake evidence is stronger than a “strict” six-week programme that routinely slips. Investigations score the gap between promise and proof.

Use the monthly compliance checklist and sample PMI dates against declared weeks before anyone else does. Recurring defects between inspections can mean the gap is too long, repairs are not sticking, or walkaround reporting is weak — investigate which, then act.

Sample interval justification note

Operator procedure: keep a short written justification with the maintenance system. It is not a GOV.UK form. It is your evidence that the week-count fits the work. Update it when you change the interval or when the operation changes materially.

Example structure (adapt to your fleet — do not copy figures as if they were statutory): fleet or class identity; typical annual mileage band; type of work and roads; age and condition summary; recent defect and prohibition trends; chosen interval in weeks; date notified on the licensing service; next review date; name of the person who authorised it.

When you shorten the interval after a prohibition or rising defects, say so plainly. A honest “shortened after PG9 trend on brakes, notified on [date]” is better evidence than silence plus a quietly tighter diary.

Common PMI interval mistakes

Fix mistakes by aligning declaration, planner and sheets, then writing the justification. Do not “catch up” by skipping inspections to reset the diary — that invents a new gap. Bring overdue assets back under control, then restore the notified rhythm.

ISO week planning in practice

Official guidance expects safety inspections inside the ISO weeks you notified, with a planner set at least six months ahead. Operator procedure: plan by ISO week numbers, not by “sometime in March”. A sheet dated in week 14 when the vehicle was due in week 12 is late against the arrangement, even if someone still calls it “the March PMI”.

Build the forward planner from the last completed inspection (or from the first declared due week for a new asset), then step forward by the notified week-count. Book the bay and any brake capacity inside that due week. If capacity cannot land in the due week, treat that as a planning failure — bring the inspection forward or fix capacity — do not silently accept week+2 as normal.

Year-end and bank-holiday clusters regularly break ISO discipline. Pre-load those weeks in the six-month planner. Move inspections earlier into quieter weeks rather than stacking everything into a closed workshop week and hoping the sheet still “counts”.

When an inspection is late, record why, complete it as soon as safe, and reset the next due from a controlled rule your procedure defines — typically from the completed date or from the original due, applied consistently. Inconsistent reset rules make the next six months of dates look random under audit.

FleetPro PMI scheduling

FleetPro stores the inspection interval you use on each vehicle or trailer and helps you plan dates against it. It does not replace declaring the arrangement on the licensing service.

PMI interval checklist

Questions operators ask

Is every HGV legally on a six-week PMI?

No. Six weeks is common practice for many fleets. The legal arrangement is the interval you notified and keep.

Who sets the inspection frequency?

The operator, based on the work, then declares and follows it. The transport manager must be able to show the system works.

Can I run longer than six weeks?

Yes if the operation justifies it, you notify it, and you keep the sheets on time. A long gap with late inspections is not a defence.

What if my planner and licence weeks disagree?

Align them. Update the licensing service when arrangements change, and make the planner match the notified weeks.

Where do PMI sheets sit in retention?

At least 15 months with the repair and brake evidence. See how long HGV maintenance records should be kept and transport manager records.

You can open a trial where the package includes maintenance planning. Start at organisation setup. Packages are on pricing.

Official sources

Guide to Maintaining Roadworthiness (opens in a new tab). Goods vehicle operator licensing guide (opens in a new tab).