A judge has warned about the dangers of driving at “excessive and unreasonable” speed after concluding that a hospital doctor who was in collision with a 12-year-old girl on a pedestrian crossing was going too fast despite being under a 30mph limit.

Deputy High Court Judge Dexter Dias heard that consultant physician Shanthi Chandran was driving her BMW i3 Range Extender at 28 mph in a 30-mph zone when the accident happened on a “dark and rainy Monday morning” on the Buckingham Road in Oxfordshire in January 2018.

He was also told that the child, who suffered a serious head injury, had stepped on to the crossing when the light was green for traffic.

But he concluded that Dr Chandran, who was on her way to work in Milton Keynes, Buckinghamshire, was driving at an “excessive, unsafe and unreasonable” speed and had failed to pay “sufficient attention to hazards and other road users”.

In a controversial ruling, the judge said there was a “common misconception” that it was “reasonable and competent” to drive “just below the speed limit”.

He said that “may not be”.

The girl’s mother had sued Dr Chandran for damages – on the girl’s behalf.

Judge Dias outlined his conclusions in a ruling published on Wednesday after considering evidence at a High Court hearing in London in April.

He said the child, who had been left with “cognitive and psychiatric problems”, could not be identified in media reports.

The judge ruled that Dr Chandran was in breach of her “duty of care” towards the child and was 60% liable for the incident.

He said the child had stepped on to a pedestrian crossing when the light was green for traffic and was 40% liable.

“While this case is not about a fatality, it shows yet again how dangerous it is to drive at excessive and unreasonable speed,” said Judge Dias in a written ruling.

“There is a common misconception that if one is driving just below the speed limit, this is sufficient to be a reasonable and competent driver.

“It may not be.

“The maximum speed limit is not a target or an infallibly safe measure.

“It is an absolute upper limit, only justified if conditions and the road situation are sufficiently good to permit it.

“This, essentially, was the error that Dr Chandran fell into.”

She alleged that the “incident” was caused by Dr Chandran’s negligence.

Lawyers representing her argued that Dr Chandran was “driving too fast” given the “prevailing conditions”.

They argued that if Dr Chandran had been driving at a “safe and reasonable speed”, the collision would not have happened.

Dr Chandran denied negligence and causation and argued that the incident was caused by the girl stepping out into the road when the “traffic light was green for vehicles to proceed”.

She said she was driving at 28 mph, which was below the 30mph speed limit, and “appropriate for the conditions” and maintained that the “liability” lay fully with the girl.

The judge heard that Dr Chandran had not been “reported by the police for any criminal offences”.

He said he had been asked to make decisions about liability – he has not made any ruling about the size of any damages award.