By Charles Pekow — If you're male, over 45, or not wearing a helmet, you’re more likely to be seriously injured in a single-bike crash than if you crash alone and don't fit into one of those categories. So found a study in Sweden. Injuries were also more severe for those cycling for recreation as opposed to going to work or school, those riding weekdays as opposed to weekends, and those on roads as opposed to bike paths. And all when no other vehicle was involved.
The researchers note, however, that their findings came from police and hospital records, which don't include unreported crashes. And a higher percentage of single-bike crashes probably don't get reported than multi-vehicle ones. One factor that didn't make a difference in the severity of the injury was whether snow or ice covered the road/trail.
Researchers couldn't explain the reasons but say that their findings suggest that safety programs need more emphasis on single-vehicle crashes and protecting older riders. See https://www.sciencedirect.com/science/article/pii/S0001457521005418 with further discussion at https://www.sciencedirect.com/science/article/pii/S2214140521003509.
And if you suffer the misfortune of crashing with a truck or bus, it's more likely to kill you in a city than in a suburb. At least that's what a study in China found. Therefore, safety programs need to focus more on restricting bus/truck traffic in cities, the researchers suggest. See https://pubmed.ncbi.nlm.nih.gov/35100072/