What I remember from driving class was that the risk factors change depending on urban, suburban, rural. In urban areas car vs pedestrian accidents are common. Accidents involving cars as you said are typically low speed accidents.

In Rural areas the opposite is true. High speed car vs car and car vs tree accidents are most common.

Though bigger doesn't equal safer. I remember someone else pointing out that large vehicles don't increase safety overall, they decrease it. If you consider two large trucks hitting each other is typically worse than two smaller passenger vehicles doing the same. It's only large truck vs small car that is slightly safer. Less than one might think because large vehicles tend to roll over more often.