Cheers! There are a few models that try to account for this bias, here is one.

I agree WRT the species/groups with very very few records, and just adding a footnote to say so.

WRT attribution for data etc, it's something I'd like to do, but haven't learnt how, yet..

Cheers!

No, iNaturalist keeps record of wild individuals, domesticated/captive specimens are excluded, records of Homo sapiens are excluded. Road traffic deaths are easily found, with breakdowns by vehicle type. Here's road traffic injuries data from the WHO, and Our World in Data.

A small minority, yes. In a study in Ontario ~3% of motorists aimed for them. 3% of the huge volumes of drivers is lots. Add to that that many snakes reach sexual maturity late, and are slow breeders, that's a disaster. In South Africa it's very common, there's an attitude of 'kill first, identify later'.

rhino = nose , rhinoplasty etc : )

But I would be shocked if there were no roadkill rhinos, a couple of years ago there was a roadkill giraffe in Kruger! People behave terribly within nature reserves.

For the niche species sure, most people don't know even insect families, let alone binomial, but common names are too fuzzy.

There's too many shared/localised common names, besides knowing the genus gives you some kind of idea of relationships.

WRT the second point, this is my second post to dataisbeautiful, I wasn't aware that could be done.

iNaturalist is for the recording of wild specimens, domesticated or captive species are excluded from the records. I think you'd find reliable numbers for dogs elsewhere (by UL law every dog is RFID chipped), but for cats it may be more difficult, many are just ditched or left to rot and the bodys never recovered.
The distinction of wild/captive is something I could have mentioned clearly.

I know. I suspect its because pheasant are such common roadkill that people don't take much notice of it. Imagine if everyone reported every squished snail! It may also be that pheasant are very light, and more quickly removed by scavengers.

Roadkill is roadkill!

Edited from the grave xD

via occiditis ?

Mammals make the largest group recorded, but probably not the largest group run over - mammals are simply easier to spot as they are large, and are probably likelier to motivate people to record their presence.
Records of invertebrates were largely uploaded by people moving on foot.
Reptiles probably make a large group of roadkill, because they are relatively slow moving, utilise road surfaces to warm up, are harder to see while driving, and may even intentionally be killed.

E: Data taken from Roadkill UK project on iNaturalist, data for other regions can be exported from Global Roadkill Observations, and the data were plotted using SankeyMATIC, though I would like to plot this in R to save time.