The appeal follows the incident in which two cars – a red Ford Fiesta and a black Mercedes – collided on Route de la Trinité at around 9.30am on Tuesday 5 March.
While the Ford Fiesta was travelling towards St Helier, the Mercedes was pulling out of Rue de la Croiserie, onto La Route de la Trinité.
Officers are seeking to speak to the driver of a white van who stopped at the scene of the collision but had left before police arrived.
CAN YOU HELP?
Anyone who may have seen the incident or who has any information is asked to contact police on 612612 or the independent charity Crimestoppers anonymously via their website or on 0800 555 111.