A district judge has called on motorists to show the "utmost awareness" on the road after jailing a retired school principal who knocked down and killed an elderly pedestrian.

Madam Law Moh Koi, 79, had been walking across a pedestrian crossing when she was struck by Kwok Kah Kuoy's Honda Odyssey at about 6.20am on Feb 8 last year. She died 10 days later of a serious head injury.

Although the traffic lights were in his favour, Kwok was 55m away when he spotted the woman, but instead of slowing down and giving way to her, he flashed his high beam at her in Marine Parade Road.

Yesterday, Kwok, 71, was sentenced to six weeks in jail and banned from driving for six years by District Judge John Ng, who convicted him on Jan 29 of causing death through a rash act.

Judge Ng said the accident "arose out of a situation created by the inexplicable act of the deceased in crossing the road with no attention paid to the red man" and "seemingly having no regard for the approaching vehicles from her right".

But he also warned that roads are shared by cyclists and pedestrians, some of whom may have limited mobility and a reduced sense of sight and sound.

"Even as our vehicles are used to get us from one place to another quickly, we must proceed with the utmost awareness that our vehicles are a potential source of grave danger," he said.

"Ultimately, it is not just a question of who has the right of way but how to make the journey in the safest possible way.

"A life lost on our roads is one life too many. We desperately need to cultivate an attitude of looking out for each other on our roads."

Deputy Public Prosecutor Peggy Pao-Keerthi told the court that Kwok was driving at 50kmh to 55kmh when he spotted Madam Law. He flashed his lights and continued driving until he was one to two car lengths away from her, then sounded his horn, veered to the right and braked - but the left portion of the car hit her.

Seeking a sentence of at least three months and an eight-year driving ban, DPP Pao-Keerthi, together with DPP Soh Weiqi, said Kwok was "sufficiently alive" to the risk of colliding with her.

Despite having four to five seconds to react before the collision, he maintained his speed and, other than flashing his high beam, did not take any action to avoid hitting Madam Law.

DPP Pao-Keerthi also pointed out that Kwok - a former principal of Ghim Moh Secondary School - was driving above the 40kmh speed limit.

Kwok's lawyers Anthony Wee and Lydia Lee said Kwok had kept a proper lookout and his failure lay in the fact that he did not manage to slow down in time.

The failure was a momentary lapse of judgment, and a short jail term of four to six weeks and five years' disqualification would be sufficient punishment for the grandfather of four, said Mr Wee.

Kwok, who uses a walking stick, had his sentence deferred to March 19. He could have been jailed for up to five years and/or fined.