If it's purely a road traffic accident (which this sounds like) and not for example to do with loading and unloading activities, then it's not RIDDOR reportable whatever the consequences.

The seven day is not applicable to the situation described for the passenger (it is the driver who is at work).

The 7 day absence is not forgotten.  It is just outside the scope of RIDDOR, same as if someone had a 7 day absence because they had an accident while ice-skating (assuming that ice-skating isn't part of their work).

Yes, sorry, I was just fantasising about the ice skating.

It is outside the scope of RIDDOR because road traffic collisions while driving or being driven on public roads are excluded from RIDDOR.

BigPub

Just because it's outside the scope of RIDDOR doesn't mean that it's not outside the scope of all health and safety legislation including, in particular, the Health and Safety at Work etc Act 1974.

So, work-related accidents during travel are recognised as a key focus for many employers. Your case involving a nurse and service user is an example of a relatively high risk scenario, where an organisation has to exercise its duty of care to its employee and to the service user.

Hence, just because it's not RIDDOR-reportable doesn't mean that it isn't worth recognising - many organisations would count it in their accident stats (though usually under a separate category to the RIDDORs) - and investigating.

It's possible that there might have been measures that were "reasonably practicable" to prevent this injury. Perhaps equally possible that there were no such measures. But if you don't do at least a rudimentary investigation you will never know.

You may have control over when and how your employees travel, whether they put pressure on the driver to speed up,  whether they put their seat belts on, whether they or your service users distract the taxi driver, which taxi firms you use, and a whole range of other factors that may or may not be relevant in any particular case, something you won't know unless you investigate.

What you can control is always the issue in cases like this. We have not been told how the person suffered the whiplash. Did the taxi break suddenly? Why did it break? Was the driver at fault? If so, are you confident that you chose the best firm to provide the service? Is it, sort of business where the drivers are desperate to make as many trip as possible so they drive do fast and literally cut corners?

If you are part of the NHS, why was patient transport not available?  Do they charge “too much”?

Somethings you have no control over, like the state of the road or the action of other drivers (another reason why the HSE want to avoid this area of responsibility). There are loads of questions to ask but where its RIDDOR or not is not part of it.

Years ago, when I was working for a government agency, we had a potential firearms incident. It was not a RIDDOR despite several enquiries from senior managers. It was investigated thoroughly and at length and action taken to make sure it never happened again. The same week a length of pipework used to distribute compressed air around the site failed. There was no risk to anybody but it was a failure of a pressure system and as such RIDDOR reportable, under the regulations. The investigation for that incident lead to a simple swift conclusion: the pipefitter was useless and he and his company was not allowed back on site. RIDDOR has nothing to do with what you and I might regard as the seriousness of the incident. It is just a list of what you must do.