What's The Likely Sentence Someone Would Receive Who Pleaded Guilty...

[sandyRoe]

...to 'Causing injury by careless driving'?
The circumstances are these: a driver comes around a corner and crashes into another car. The driver of this car suffers a broken arm and a broken ankle.
This happened about 9 months ago and the arm appears to have healed but not so with the ankle.
Who decides whether driving is careless or dangerous in circumstances like this?

[Buenchico]

Quotes:
"The offence of driving without due care and attention (careless driving) under section 3 of the Road Traffic Act 1988 is committed when the defendant's driving falls below the standard expected of a competent and careful driver - section 3ZA(2) of the RTA 1988"

"The offence of dangerous driving under section 2 of the Road Traffic Act 1988 is committed when the defendant’s driving falls far below the standard expected of a competent and careful driver and it would be obvious that driving in that way would be dangerous – section 2A of the RTA 1988."

[Source: https://www.cps.gov.uk/driving-offences ]

While there is a specific offence of "causing serious injury by driving dangerously" (section 1A Road Traffic Act 1988), there's no specific offence of "causing injury by careless driving" (as in your post). Such an offence would be dealt with purely as "careless driving" but with the injury thus caused pushing the 'harm' factor (considered by the court when passing sentence) into the 'higher' category. See pages 114 to 116 here fo rthe sentencing guidelines:
https://www.sentencingcouncil.org.uk/wp-content/uploads/MCSG-April-2017-FINAL-2.pdf

[sandyRoe]

You drive round a bend on the wrong side of the road and crash, seriously injuring another person, and someone decides that's not dangerous driving.
Funny old world.

[ToraToraTora]

that sounds like it should be at least DWDCAA and possibly dangerous driving sandy, are you saying was not actually deemed as such? Not sure I'm getting your meaning at 18:39