Don't look too far: 'over'pants can be worn over regular pants. For anyone who likes to navigate through traffic jams, commutes by motorbike or just enjoys the ride, but doesn't want to show up at the rendezvous in a complete motorbike suit afterwards. Motorbike overpants are easy and quick to put on over regular pants. No need to change outfit in the toilet stalls.
With this objective in mind, most motorcycle overpants have long zippers which run over the entire length of the legs. Because even manufacturers know that overpants are often used as extra protection in less favourable weather, they are wind- and waterproof. Thanks to the right membrane.
The question mark is there for a reason. You can't want everything. The overpants should go smoothly over your regular pants, but which one you prefer is hard to predict. Comfort and protection come before looks and style, in this case. We shouldn't exaggerate, though: the time of flared pants is over and hip boots ... well.
Knee protectors are standard in all motorcycle pants, the same as with overpants. Hip protection is often optional, although in that case the necessary space is provided. In motor pants - as in most motorcycle clothing - the zipper is the weakest part, and of course there are two of them, over the entire length of both legs.
If you prefer more safety, perhaps you should take a look at motorcycle jeans. These have rapidly evolved into a look which hardly makes you suspect that they are full-blown motorcycle pants. Lack of waterproofness can be solved with rain pants.
The outer fabric and the membrane of motorcycle clothing are more demanding than, say, a T-shirt or a pair of socks. Everything is possible, but specific maintenance products for motorcycle clothing are no marketing trick.
General detergents can damage the properties of membranes and outer fabrics, so always take a close look at the information for maintenance of motorcycle clothing.