I haven’t yet ridden a velomobile (though I may purchase one soon and am planning on building one for riding round Australia and living out of for a year or so), but I’ve been riding a recumbent tricycle (Greenspeed GT3 Series II) since 2014, including various touring in Australia (Victoria and some South Australia), America (through California, and from St Louis to Philadelphia) and New Zealand (Auckland to Kaikoura¹).
People often assume that the trike is more dangerous than an upright bike because of being lower, and there is some truth in that aspect, but on the balance of things I consider and find it much safer than an upright bicycle. The increased width increases visibility again somewhat; the fact that the maximum width is at ground level rather than over a metre up means that you can’t ride in the gutter as bicyclists often do and have to be further out from the edge of the road, which makes you much more visually distinct (rather than blending in with the edge); the fact that you’re necessarily further from the kerb makes it so that in many places cars can’t sneak by you dangerously close and have to be more considerate in how they overtake; you the cyclist are far more aware of how traffic is flowing due to your posture (constantly beholding the world in front of you rather than craning your neck painfully from time to time, and with a mirror² in which you can also constantly monitor what’s coming up behind) and so can interact more usefully with it (which is a massive deal for safety). I always run at least one flag, and when heavily laden drape the back of one of my old hi-vis orange shirts over the back of my load. Combine all that with the inherent stability (which incidentally helps you to go in an actually straight line), the greater comfort, the low centre of gravity and a few other such factors, and I feel very significantly less safe when riding an upright bicycle (road or mountain), as I have a handful of times since getting my trike.
Recumbent bicycles (as you seem to be showing talking of in part) I have no experience with; they indeed have some notable problems for casual use, and are more suited for racing. When talking of velomobiles, make sure you’re considering their tri- or quadricycle basis, as distinct from two-wheeled speedliners which have a tendency to amplify some of the problems or hazards of recumbent bicycles even further. Of velomobiles in general compared with recumbents, I have heard some people reporting that traffic sometimes interacted with them more like a strange small car than like a strange bicycle, and that they felt slightly less safe.
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¹ At Kaikoura just a couple of weeks ago I suffered unexpected and unexplained sidewall failure in my rear tyre, upon which I discovered that literally no one in the entire country stocks 349mm tyres—the national Schwalbe distributor, for example, doesn’t import anything below 20″. So instead of cycling the rest of the way to Christchurch I took a bus, and on returning to Australia last week equipped a spare I had, and I can buy more.
² On uprights, mirrors don’t tend to work well for lack of suitable attachment points and techniques, but on recumbent tricycles they work much better, and on recumbents in general mirrors are nigh essential as seeing behind otherwise takes leaning forwards out of your seat a fair way in order to twist your body enough to see behind adequately.