I'm not saying the risk is zero: as I was at the cinema last night with a close friend of one of Fred West's victims, who was abducted and killed during a trip home from university, it would be stupid to do so.
However, the point is that hundreds of children are killed and severely injured by or in cars (the main risk in car parks, as it happens: I worry about my children in car parks, because of the cars), maimed by senseless domestic accidents with boiling, corrosive and poisonous liquids and killed and paralysed in sports accidents. These are accidents that are in many cases preventable, and are probably reducing overall because of better seatbelts, more routine 'childproofing' both of houses and of individual containers, and better safety processes in sports. But they happen, and will continue to happen.
Children are also routinely abused, sexually and otherwise, within families and extended family settings, along with (perhaps, although we don't know, less than in the past) settings like schools and churches. Certainly, child protection processes in such settings have improved, and although professionals I'm sure would in some ways prefer a return to the days of deference, the unwillingness of parents to defer to authority is a very a good thing indeed in terms of dealing with potential abuse in institutional settings.
But for all that, there is a steady drumbeat of children being harmed, sexually and otherwise, by strangers who abduct their prey. The number normally quoted is about ten a year, which is about a one in a million risk for each child per year, with the death rate a small fraction of that. If you drive your child two hundred miles, or take a plane flight to a holiday in Spain, that's about an additional one in a million risk of death. Clearly, sexual assault has far deeper emotional resonance than a car accident, but in most circumstances a 1 in a million chance of death is in considered small.
Humans aren't very good about reasoning about risk. There's a certain amount of risk acclimatisation, which means that you are happy to live with risks that are familiar, even though they are in reality quite high (cars, boiling water). When the risk is very low, but the outcome extremely unpleasant, we tend to regard the risk as larger than it really is. This is especially true when it's one we can't really control: we all feel that we're better drivers than average, which is why people worry more about planes and trains (safer, but you're not in control) more than cars (much more dangerous, but you're more able to make a difference). Sex assault by stranger is frightening because we feel that there's little we can do.
But wearing a seatbelt, driving a car with anti-lock braking (probably the single most important car safety measure both for passengers and pedestrians in the past few decades), not flying on third-world airlines and avoiding standing in the leading and trailing cars of a train are all safety measures we can take for ourselves, depending on our risk appetite, which have almost no downside. There's no conceivable scenario on the road (as opposed to a rally stage) where ABS is bad for you. Fear of sex assault does have a downside, because it paralyses scout groups and fishing clubs and the willingness of people to offer help to distressed children.
Last week I was out on a bike ride and I came across a child weeping on a street corner with a scooter lying on the ground. I was on my own, in a quiet area, with no other adults around so I rode on 400 yards, stopped, and phoned the police. That cannot, cannot, be right. My neighbour did not let her daughter walk to school on her own, even at 18 (my daughters get a bus across town and have done since 11). A parent who points out that they went to university interviews in the 1980s on their own and therefore their children can bloody well get a train is held to be taking unreasonable risks, even though mobile phones mean the risks are rationally far lower (I bet many people here made long train journeys on their own in their early teens: what's changed, so that children are now almost always accompanied to open days?)
The culture of fear of abusers, and "risks" more generally has a real downside. Trying to be rational has you slated as heartless, but it has to be done, as we are raising children who have entirely miscalibrated risk appraisal.