Is it unfair for the rule to erode the safety advantage of people in large, new cars?
Arguably not — a large part of that advantage was bought at other road users' expense in the first place, and nobody has a claim to an advantage of that kind.
The question "everyone must benefit — compared to what?" is the crux. The safest people are those who, wherever possible, travel only in heavy, new cars. But their safety lead results at least partly from factors that reduce their own risks at the cost of others: both the decision to use large, heavy vehicles (which are more dangerous to everyone they hit) and the decision to travel by car wherever possible.
Against that background the paper doubts that it really constitutes an unacceptable "instrumentalisation" when injury-minimising programming relativises such safety advantages, and gives two reasons:
- The people affected have no entitlement to those safety advantages. You cannot be wronged by losing something you had no claim to.
- The existence of safety advantages obtained at others' expense is, if anything, a reason to criticise the status quo — not the new rule. It is no deficit of injury-minimising programming that it relativises this somewhat.
The conclusion is carefully hedged: if what happens is merely that an unearned advantage is levelled out, then under certain circumstances that is indeed justifiable.
Notice the shape of the move, because it recurs across applied ethics. An objection of the form "your rule makes me worse off" only has force once we know what baseline the comparison uses. If the baseline itself embeds an unjustified privilege, then losing ground against it is not a harm but a correction. The hard part, as ever, is agreeing on which baseline is legitimate.
Go deeper:
Wikipedia: Risk compensation — the evidence that safety advantages change behaviour, which is part of why the baseline is contested.