FREE CHAPTER from ‘Low Velocity Impacts in Road Traffic Accidents: Law and Practice’ by Jake Rowley


What is meant when we refer to a ‘low velocity impact1’ claim (or ‘LVI’ for short)?

Such terminology is used in conjunction with claims arising out of a road traffic accident (‘RTA’) in which a Defendant alleges that the collision was so minor or insignificant in its nature that it was incapable of causing any occupant(s) of the vehicle any injury whatsoever or, often asserted in the alternative, that the nature of the collision was such that it was inherently unlikely that any occupant(s) of the vehicle did, in fact, sustain any injury.

Legally speaking, a defence which asserts that the collision was a low-velocity impact is a challenge to the causation of injury.

The issue arises most commonly (although by no means exclusively) in claims in which it is alleged that the Claimant sustained soft-tissue/whiplash type injuries to the neck, shoulder(s) and/or back. Given the prevalence of such injuries in LVI type cases it is in relation to these sorts of injuries that this publication focuses its attention, however the observations made apply equally to any injury which might have been allegedly suffered in a LVI type collision.

It is generally accepted that in order for an occupant of a vehicle to sustain soft-tissue/whiplash type injuries to their neck/shoulder(s) and/or back they must experience a degree of occupant displacement within the vehicle in which they are travelling i.e. that is to say that their body must be physically moved/jolted by the impact caused by the Defendant’s vehicle.

In simple terms, a LVI defence is one in which the Defendant argues that the circumstance of the collision, together with any other evidence which may have been collated, collectively demonstrate or tend to suggest that the forces transmitted between the Defendant’s vehicle and the Claimant’s vehicle, at the point of collision, were insufficient to cause occupant displacement or, as a matter of fact, did not cause such occupant displacement, and thus, the collision was incapable of causing any injury. This impartation of force is often referred to in the relevant authorities and elsewhere as the ‘v’ (i.e. ‘velocity’) or ‘ v’ [“delta v”]2 i.e. the change in velocity – the force which is actually transmitted to/experienced by the Claimant’s vehicle and thus the Claimant, by reason of the impact.

In order to make good the assertion that a collision was incapable of causing injury Defendant’s often rely on a variety of evidence from varying sources, including: (i) an account from the Defendant driver him/herself as to the movement of his/her vehicle immediately before, and at the time of, impact; the speeds involved; how he/she experienced the collision etc.; (ii) photographic evidence of damage to the vehicle and/or their positioning post-accident; (iii) expert engineering evidence; and (iv) medico-legal evidence. The ultimate goal for any Defendant is, essentially, to present to the Court a persuasive account of an insignificant, mere touching of the two vehicles.

Although long-standing and reasonably common place, defences asserting LVI are not without their controversy or difficulties. It is beyond the scope of this publication to consider the specific medical and technical engineering detail relating to LVI cases. What can be said, however, is that whilst general understanding of this particular field (sometimes referred to as ‘biomechanics’) has greatly improved, there are still wide divergences of respectable opinion in relation to critical issues that arise in such claims. By way of illustrative example: there continues to be serious disagreement between experts as to whether there is, in fact, anyv’ figure below which it can be reliably concluded that injury becomes unlikely/highly unlikely/impossible; with some arguing that no such figure even exists. Whilst it may be possible to ascertain, scientifically, the level of force transmitted from one vehicle to another (by assuming various speeds, point of impact, specific vehicle bumper specifications etc.) some point to a long list of other variable factors which, it is argued, have a bearing on whether injury is, or is not, likely to be suffered by an occupant of the vehicle. These include:

  • A Claimant’s age;

  • A Claimant’s gender;

  • A Claimant’s previous medical history (both generally and in relation to spinal conditions specifically);

  • A Claimant’s general vulnerability to injury;

  • A Claimant’s previous accident history;

  • Whether a Claimant was aware of the impending collision and/or whether he/she was braced at the point of impact, or not;

  • The precise position of a Claimant’s head/neck at the point of collision;

  • The presence/absence of head restraint;

  • The age of the Claimant’s vehicle;

  • The design and construction of the Claimant’s vehicle’s bumpers;

  • The angle and precise position of impact from the Defendant’s vehicle.

Given there is no consensus on whether there is actually a ‘v’ figure below which it can reliably be concluded injury is unlikely, it is wholly unsurprising that there also continues to be disagreement on what any such ‘v’ figure actually is. With such crucially important matters still being the subject of ongoing academic and expert debate, it is easy to see why LVI cases are not entirely straightforward.

Furthermore, LVI issues routinely arise in low value personal injury claims which, on their face, would objectively warrant allocation to the Fast Track given the value of injuries alleged. However, a Defendant’s desire for expert evidence to support an allegation of LVI has ultimately led to LVI defences causing a number of case management difficulties vis-à-vis appropriate track and permission for expert evidence, which has required the Court of Appeal’s consideration on more than one occasion. This publication considers the two key Court of Appeal decisions later, in Chapter 4, and the way in which LVI defences should be approached procedurally.


1Sometimes also referred to as a ‘low speed impact’ or ‘LSI’ (for short) [although such description is, probably, inaccurate given the concern is with the forces transmitted as between the two vehicles, and not simply the speed that one/other/both are moving at]

2i.e. the change/difference in ‘v’ – velocity