What is an EAPC, and when does a modified bike stop being one?
An EAPC — an electrically assisted pedal cycle — is an e-bike the law treats like an ordinary pedal cycle. To count as one, the Government says the motor must have a continuous rated power output of no more than 250 watts, it must stop propelling the bike once you are going faster than 15.5mph, the bike must have pedals you can actually ride it with, and the rider must be 14 or over. That definition sits in the Electrically Assisted Pedal Cycles Regulations 1983, as amended by the 2015 Regulations that came into force on 06/04/2015.
Notice that none of it is about how the bike left the factory. It is about what the machine is on the day you ride it. So a bike that was a perfectly lawful EAPC when you bought it can quietly stop being one later — and that is the harder question, the one a bare list of the rules never answers. If you want the categories rather than the change, we set those out on illegal e-bikes and liability.
Which modifications actually cross the line?
We would look first at whether the change touches one of the three things the definition turns on: power, the speed cut-off, or the need to pedal. A change that touches none of them — a different saddle, better brakes, a rack — does not affect the classification at all. Changes that can take a bike outside the EAPC rules include:
- Derestriction. Removing or overriding the cut-off so the motor keeps assisting past 15.5mph. This is often a setting or a small in-line device rather than a visible part, which is exactly why it is missed.
- A more powerful motor, or a conversion kit. If the continuous rated power of the fitted motor exceeds 250 watts, the bike is outside the definition however it is ridden.
- A throttle that drives the bike along. Government guidance is that approval is needed where a machine can be propelled up to 15.5mph without pedalling — a “twist and go”.
- Removing or disabling the pedals, so the bike can no longer be propelled by pedalling at all.
The Office for Product Safety and Standards puts the consequence bluntly in its guidance for e-cycle users: a device modified so that it exceeds the legal limits is “an unregistered motorbike in law”. The same guidance warns that modifying the motor or battery increases the likelihood of a fire, which is a second problem sitting on top of the first.
What changes after a collision when the bike is no longer an EAPC?
The classification is not a technicality. It moves the machine into a different legal box, and that box has different rules attached. Under section 185 of the Road Traffic Act 1988 a motor vehicle is a mechanically propelled vehicle intended or adapted for use on roads — and it is the word “adapted” that catches a converted bike. Once a machine is a motor vehicle:
- Insurance is compulsory. Section 143 of the same Act says a person must not use a motor vehicle on a road or other public place without a policy of insurance in force. Almost no converted e-bike has one.
- Registration, tax, a licence and a helmet come with it. The Government's own guidance is that a bike which is not an EAPC must be registered and taxed, and that the rider needs a valid driving licence and a motorcycle helmet meeting British safety standards.
- Fault arguments change shape. If you were riding the modified bike when you were hurt, a claim against an at-fault driver may still be possible, but the other side can be expected to raise the classification — usually as contributory negligence, sometimes as more than that. It is fact-sensitive, and it is not something we would want anyone to judge for themselves.
What if I was hit by a modified e-bike?
If the machine that hit you should have been insured as a motor vehicle and was not, that may open a route that is closed to you against an ordinary cyclist. The Motor Insurers’ Bureau agreements exist for exactly the situation where a vehicle that ought to have been insured was not, or where the person responsible cannot be traced. Whether they apply to a particular machine turns on the facts, and on the classification — which is why the evidence below matters as much to a pedestrian as it does to a rider. We set out how that route works on our page about uninsured and untraced drivers, and how fault is argued between a bike and someone on foot on our page about e-bike and pedestrian accidents.
What evidence decides the classification?
This is the part to act on first, because it is the part that disappears. Within a few weeks of a collision a converted bike is usually repaired, stripped for parts, quietly put back to standard or simply thrown out — and once the motor or controller has been swapped, no one can answer what the machine was on the day by looking at it. If you do only one thing, do this: keep the bike, unrepaired and unaltered, and put it in writing that you want it preserved.
What tends to settle the point:
- The motor and controller markings. The continuous rated power is usually stamped or labelled on the motor casing, and the controller's voltage and current rating sits alongside it.
- The display, app or firmware settings. Many systems store the speed limit, the wheel-size setting and a trip history. A derestriction is frequently a stored setting, not a part — photograph the settings screens before anyone resets them.
- Any in-line device fitted between the motor, the sensor and the controller. These are small, easily removed, and are the single most commonly lost piece of evidence.
- The paper trail for the kit or the bike. The listing you bought from, the invoice, the packaging, the instructions, and the declaration of conformity — Government guidance says a conversion kit should come with one, and its absence is itself worth recording.
- Who did the work. A shop invoice, a job sheet, a booking confirmation or a message thread. This is often what identifies a responsible party who is not the manufacturer.
- The battery and charger. Whether the pack and charger were the ones the drive system's maker authorised, or a substitute. Government guidance is that incompatible battery packs and chargers can cause an extremely high fire risk, and that spares should be genuine items authorised by the e-cycle or drive-system manufacturer.
- Scene material. Photographs taken before the bike was recovered, dashcam or CCTV footage showing the speed it was travelling, the police reference, and any vehicle examination carried out.
If a component failed as well as being unlawful — a brake, a controller, a battery — the same physical evidence supports a second, separate route. We cover that on our pages about faulty e-bike accidents and e-bike battery fire claims.
Who is the responsible party for a modification?
A converted bike usually has more than one candidate, and identifying the right one is the whole job. Part I of the Consumer Protection Act 1987 is the starting point for the hardware. Section 2 makes liable, for damage caused by a defect in a product, the person who manufactured it, anyone who holds themselves out as its producer by putting their name or mark on it, and whoever imported it into the United Kingdom in the course of business to supply it on.
Section 2(3) is the provision that does the practical work when a kit or battery arrived from a marketplace listing with no traceable maker behind it. Put shortly: where someone injured by the defect asks the supplier to identify the producer, own-brander or importer, and the supplier neither does so nor identifies who supplied it, the supplier can find itself liable instead. That is why we put so much weight on the paper trail — a request made properly, and in time, is what can turn a nameless seller into an answerable one.
Alongside that, and depending entirely on the facts, there may be:
- Whoever carried out the conversion, if the work itself was done without reasonable care — a shop, a trader, or a private seller who converted the bike before selling it on.
- The seller of the bike as converted, where it was sold already modified and presented as something it was not.
- The battery or charger producer. The statutory guidelines on lithium-ion battery safety for e-bikes, published on 12/12/2024 under the General Product Safety Regulations 2005, record that those Regulations apply to all lithium-ion batteries for e-bikes, including those sold for use with or as part of a conversion kit.
- A driver, or a highway authority, where the modification was not what caused the collision at all. A bike being non-compliant does not make someone else's negligence disappear.
Do the 500W and throttle rules people mention apply?
No — and this one comes up often enough to be worth saying plainly. In 2024 the Department for Transport consulted on two changes: raising the maximum continuous rated power for an EAPC from 250 watts to 500 watts, and allowing twist-and-go throttle assistance up to 15.5mph without type approval. In the consultation outcome, updated on 28/01/2025, the department recorded that it would not take forward the proposals it had consulted on.
They were proposals, and they were dropped. The 250-watt and 15.5mph rules have not changed. A bike built or converted to those abandoned figures sits outside the EAPC rules today, whatever a seller’s listing still says about it.
How long do I have?
For a personal injury claim in England and Wales, section 11 of the Limitation Act 1980 gives three years from the date the cause of action accrued or, if later, the date of knowledge of the injured person. Where the claim is brought under Part I of the Consumer Protection Act 1987 — the product route above — section 11A applies instead: three years, subject to a longstop of ten years from the relevant time, which can matter for an older bike, kit or battery. Different rules apply to children and in some other situations.
The time limit is rarely the pressing problem here, though — the evidence is. Three years is no help at all if the bike went to the tip in the first month. Treat preserving the machine as the urgent job, and the limitation date as the outer boundary rather than the deadline you work back from.