...of all kinds!
As a daily commuter, my biggest fear and one that I've seen more than once, is to have a ladder come off the rack of a contractor's pickup or van. One that I saw came off lifted from the front and when one end hit the ground it did several end-over flips! A couple of others slid or rolled as cars hit them and they did serious damage to a series of cars in two lanes. A car would hit the damned things and they would spin until being hit by another car - totally unpredictable where they'd go next. In heavier traffic, I've had a car in front of me straddle one and if I'd been following the center of the car, I would've taken the ladder straight-on.
Then we have the trucks and vans dropping the usual paint buckets, carpets, mattresses, bags of trash, furniture, debris flying out of pickups, and other ***** that keep commuting interesting.
Bob