A preventative maintenance inspection (PMI) is the planned, recorded safety check of a vehicle or trailer carried out at set intervals to confirm it is roadworthy between annual tests. If you hold an operator licence, you signed an undertaking to keep your vehicles fit and serviceable, and the PMI is how you prove you are doing it. Skip it, record it badly, or let defects ride through, and that undertaking is the first thing a traffic commissioner will hold against you.
This guide sets out what a preventative maintenance inspection has to cover, how to set inspection intervals, why brake testing now sits at the centre of every safety inspection, and what DVSA expects to see in your records at audit.
What a PMI is and why your operator licence demands it
The PMI, more formally the safety inspection, is the core of the system DVSA describes in the Guide to Maintaining Roadworthiness. It is not a service and it is not the MOT. A service keeps the vehicle running. The annual test is a single roadworthiness snapshot once a year. The safety inspection sits between those tests and confirms the vehicle will stay legal and safe up to the next inspection date.
Your obligation comes from the operating licence itself, granted under the Goods Vehicles (Licensing of Operators) Act 1995. When you applied you gave undertakings to inspect your vehicles at stated intervals and to keep proper records. Those undertakings are enforceable. DVSA and the traffic commissioner treat a weak inspection regime as a direct compliance failure, not a paperwork niggle. The duty applies whether you maintain in-house, use a contractor, or run a mixed arrangement.
Setting your inspection frequency: time-based or mileage-based
There is no single legal interval. You set a frequency that suits your vehicles, your loads and your operating conditions, then you stick to it. DVSA expects inspections to follow a time-based pattern where practical, planned at least six months ahead, usually scheduled by ISO week number so nothing slips through the gaps.
Mileage-based programmes are allowed and often make more sense for high-distance trunking work, but they must still be tied to a maximum time interval. You record the equivalent time frequency, capped at 13 weeks, so a low-mileage month never leaves a vehicle uninspected for a quarter of the year.
The interval is a judgement based on the age of the vehicle, expected mileage, type of work and how quickly components wear. The following table reflects the typical bands in the DVSA guidance.
| Operating conditions | Typical safety inspection interval |
|---|---|
| Light loads, good roads, low mileage | 10 to 13 weeks |
| General haulage and trunking | 6 to 10 weeks |
| Arduous work, constant heavy loads | 4 to 6 weeks |
| Off-road, tipper, demanding environments | 4 weeks or shorter |
| Vehicles and trailers 12 years and older | 6 weeks maximum |
Whatever interval you declare on your licence, it has to match what actually happens. If you tell the traffic commissioner you inspect at six weeks, your forward planner and your completed sheets need to show six-week inspections, not eight or ten when the workshop got busy. Review the frequency if a vehicle’s MOT pass rate slips, if it starts collecting roadside defects, or if you change the work it does.
What a preventative maintenance inspection actually checks
The scope of a PMI must at least cover every item assessed at the annual test, using the methods set out in the relevant DVSA inspection manual (the IM) for HGVs, PSVs or trailers. That is the floor, not the ceiling. The inspection sheet should be drawn from those manual items so the inspector checks the same components, to the same standard, that DVSA would apply at test.
A competent safety inspection covers, as a minimum:
- Brakes, including a measured performance assessment (covered below), brake components, hoses, chambers, ABS/EBS warnings and air build-up
- Steering and suspension, including play, springs, air bags, dampers and mountings
- Tyres and wheels, including tread, condition, pressures, matching, valve condition and wheel security
- Lighting, indicators, markings, reflectors and electrical connections
- Chassis, body, cab security, mirrors and visibility aids
- Exhaust, fuel system and any visible fluid leaks
- Coupling gear, landing legs and trailer-specific items where applicable
- Driver controls, seat belts, horn, washers and wipers
- Any non-testable items your operation needs, such as Direct Vision Standard equipment or tail-lift checks
Every item should be marked off individually. A sheet that just says “pass” at the bottom is worthless at audit. The inspector needs a sound working knowledge of the inspection manual and the authority to fail items, not just tick them.
Safety inspection vs routine service vs MOT
| Safety inspection (PMI) | Routine service | Annual test (MOT) | |
|---|---|---|---|
| Purpose | Confirm roadworthiness between tests | Keep the vehicle running, replace consumables | Statutory annual roadworthiness check |
| Frequency | Your declared interval (e.g. 6 weeks) | Manufacturer schedule or mileage | Once a year |
| Who does it | Competent inspector, in-house or contracted | Workshop or technician | DVSA at an ATF |
| Records kept | 15 months minimum | Good practice to retain | Test certificate retained |
You can combine a service and a safety inspection on the same visit, but they are separate jobs with separate records. Do not let a service tick-sheet stand in for a proper PMI report.
Brake testing at every safety inspection
This is where many operators come unstuck. DVSA now expects every safety inspection to include a brake performance assessment, using a calibrated roller brake tester (RBT), an approved electronic braking performance monitoring system (EBPMS), or a decelerometer with temperature readings. A visual brake check on its own is not a performance assessment.
The RBT is the most effective method because it measures each wheel individually and shows imbalance across an axle. The headline minimum efficiencies measured are a service brake of at least 50%, a secondary brake of at least 25%, and a parking brake of at least 16% for HGVs. Those figures come from the braking requirements behind Regulation 18 of the Road Vehicles (Construction and Use) Regulations 1986, which requires every part of the braking system to be maintained in good and efficient working order and properly adjusted.
The big shift is laden testing. An empty roller brake test tells you very little, because the brakes are not being asked to do real work. DVSA expects brake tests laden wherever practicable, with a minimum of four laden assessments per vehicle per year spread evenly, and the annual test can count as one. The vehicle should normally be loaded to at least around 65% of its design axle weight for a meaningful result. Where a laden test genuinely is not practical, you need a written risk assessment explaining why, reviewed by a competent person, not a blank space on the sheet.
A proper RBT works through the service brake, then the secondary, then the parking brake, with the operator repeating efforts to reach maximum pedal force. You can present a vehicle for an RBT up to 14 days before the safety inspection date, which gives room to book a test facility without breaking the schedule. Whatever the result, the print-out gets filed with the inspection sheet and any deficiency gets actioned. A brake test that flags imbalance and then sits in a drawer is worse than no test at all, because it proves you knew.
Driver walkaround checks and the defect loop
The PMI is periodic. The daily defence is the driver walkaround check, and DVSA expects at least one every day, or once in any 24-hour period the vehicle is used. It covers the whole vehicle or combination, inside and out, for everything that can be safely checked without workshop equipment.
The system only works if defects close the loop. A defect report needs to capture:
- Vehicle registration or fleet number and the date
- The defect or symptom reported
- The name of the person reporting it
- Who it was reported to
- The assessment of the defect
- The rectification work carried out
- The date that work was completed
Defect reports must go to someone with enough authority to act, including taking a vehicle off the road. Keep driver defect reports for at least 15 months. Nil-defect reports should be kept for at least 3 months. A folder of nil-defect slips with no genuine defects ever recorded is a red flag to DVSA, because no fleet runs perfectly clean.
Wheel and tyre management
Wheel security is a frequent prohibition and an occasional headline-grabbing failure, so it gets its own discipline. Any time a road wheel is removed and refitted, the wheel nut torque must be re-checked, either after the vehicle has stood for 30 minutes or after it has run between 40 and 80 km (25 to 50 miles). Every re-torque check has to be recorded and kept on file. A torque mark line painted across the nuts is a useful visual aid but it does not replace the recorded re-torque.
On tyres, watch matching, tread, pressures and condition at every inspection, and remember the age rule: tyres more than 10 years old must not be fitted to the front steered axle of an HGV, bus or coach, or as single wheels on a minibus.
Record keeping and the 15-month rule
Records are what turn good maintenance into a defensible compliance position. Safety inspection records must be kept for at least 15 months, and that applies to vehicles you have taken off the licence, sold or scrapped, not just the ones still on the fleet. The same 15 months applies to driver defect reports and to wheel re-torque records.
A complete maintenance file for a vehicle should let an auditor reconstruct its whole history:
- The forward planner showing inspection dates set six months ahead
- Completed safety inspection sheets, item by item, signed and dated
- Brake test print-outs tied to each inspection
- Driver defect reports and the rectification record for each
- Wheel re-torque records
- Invoices or job cards for repair work, matching the defects raised
The detail that catches people out is closure. An inspection sheet listing a defect needs to show that defect being fixed, with a date, and the vehicle should not have run in service in between unless the fault was genuinely minor. Gaps, missing brake tests and open defects are exactly what an examiner looks for.
What DVSA looks for in an audit or at public inquiry
Whether it is a desk-based audit, a maintenance investigation visit, or a public inquiry, the examiner is testing one thing: does your paperwork show a system that actually keeps vehicles roadworthy. The common findings that damage operators are:
- Inspection intervals that drift longer than the figure declared on the licence
- Missing or empty brake tests, and no laden testing or risk assessment
- Defects recorded but no proof of repair, or repairs with no matching defect
- Records that cannot be produced for the full 15 months
- Pages of nil-defect reports with no real defects ever found
- Inspection sheets signed off by someone with no real competence in the IM
A tidy, consistent maintenance system, with a named responsible person and a transport manager who genuinely oversees it, is the strongest evidence you can put in front of a traffic commissioner. If you are not certain your records would survive that scrutiny, fixing it now is cheaper than after a prohibition. For more on who carries that responsibility, see what an external transport manager does and the transport manager requirements.
Frequently asked questions
How often should a HGV have a PMI?
There is no single fixed interval. You set a frequency to suit the vehicle and the work, typically between 4 and 13 weeks, and declare it on your licence. General haulage often sits at 6 to 10 weeks, arduous work at 4 to 6 weeks, and vehicles 12 years and older should not exceed 6 weeks. Whatever you declare, your actual inspections have to match it.
Is a PMI the same as an MOT?
No. The MOT, or annual test, is a once-a-year statutory check carried out by DVSA. A PMI is your own scheduled safety inspection carried out at shorter intervals between tests. The PMI should confirm the vehicle will stay roadworthy until the next inspection, which is a higher ongoing standard than a single annual pass.
Do I have to do a laden brake test?
DVSA expects brake performance to be tested laden wherever practicable, with a minimum of four laden assessments per vehicle per year, and the annual test can count as one. Where a laden test genuinely is not possible, you must keep a written risk assessment, reviewed by a competent person, explaining why.
How long must I keep maintenance records?
Safety inspection records, driver defect reports and wheel re-torque records must be kept for at least 15 months. That includes vehicles sold, scrapped or removed from the licence. Nil-defect reports should be kept for at least 3 months.
Can I run a PMI system without an in-house workshop?
Yes. Many operators contract inspections to a commercial workshop or use a maintenance provider, and that is perfectly acceptable as long as the intervals, scope and records meet the standard. The responsibility to oversee it still sits with you and your transport manager.
How ETM helps you keep maintenance compliant
Getting a PMI regime right is as much about oversight as it is about spanners. External Transport Manager connects operators and fleets with verified, experienced external transport managers and compliance specialists who can review your inspection intervals, audit your records against the DVSA standard, and put right the gaps before an examiner finds them. If you are setting up a maintenance system, preparing for an audit, or facing a public inquiry, the right person can make the difference between a clean bill and a curtailed licence. Start a support request to be matched with a verified transport manager, or find a transport manager directly.