Unfortunately, I have no direct experience of enforcement, as mentioned above. I do however, know of several NRPs (as well as DP), who, in the course of a contact order, have raised the driving/travel issue. It'd seem that if the judge/magistrate is enlightened, and, if they agree that one party doing all the travel is having a negative impact on the children (e.g. reduced contact due to cost/time, late to bed, early mornings etc), they will ask the PWC why they are unwilling to help find a solution which is most beneficial for the kids. At this stage, it's inevitable that the PWC will raise objections .... obviously, if they are genuinely at work they'd normally be looked at sympathetically, but in many of these cases, the NRP will often have evidence (texts, emails) about contact where the ex has stated stuff like "don't see why I should help", "I'm not doing you a favour you bastard" and other such lovely epithets where it's clear that spite, not affordability or health is what's behind their attitude. I also know of PWCs who've pleaded poverty but whose objections have been ignored as they take 2 holidays a year etc.
I guess whether or not a shared travel order is made boils down to individual circumstances .... e.g. who moved, who created the distance, and why. Clearly it wouldn't be ordered if someone really can't drive but obviously where cases like these end up in court it's usually because of a lack of co-operation over contact with travel being just part of an overall problem. If the PWC was normal and fair, but with a genuine health problem, it's highly unlikely she'd end up in court "just" over not driving.
There is of course no guarantee that a judge will order shared travel but some do and I think it's definitely worth a shot. In our case, we definitely can't afford the petrol and the ex's lifestyle is head and shoulders above ours, so considering SHE made the move - along with false promises about meeting etc - I think it's more than fair that she should meet DP halfway. She certainly has far more disposable income than we do. However, like I said, my DP made the fatal mistake of allowing the situation to drag on for too long meaning that she could whinge about disruption to her routine and get away with it as DP had been "willingly" (so the court could claim) paying all travel expenses for years. The fact WE can't afford it - and we really can't - seems irrelevant, as does the effect upon OUR daughter as we "have" to spend money or else DP wouldn't see his kids.
So - if an order is made, the PWC would then technically be in breach of that if she started making excuses about why she couldn't meet. This is where the whole court order system falls down as very few judges seem willing to impose sanctions on PWCs who break orders. A lot of orders have penal notices attached but these are rarely used. You just hope that the threat of being taken back to court would be enough of a deterrent for the PWC to obey the order but really, the system stinks and IMO there is little real support for NRPs whose exes mess about with all aspects of contact.