A fourth person was detained on suspicion of assisting an offender.
The accident happened around 8.45 p.m. last night (27/07) in the town’s Station Road area.
The victim, a man in his 30s, is in critical condition at Southmead Hospital.
The driver of the car involved in the accident fled the scene, but the vehicle, a white Ford Fiesta, was later discovered abandoned.
Officers responded to an address in town this afternoon (28/07) and arrested a 20-year-old man, a 21-year-old woman, and a 15-year-old boy on suspicion of attempted murder. A 40-year-old woman was also arrested on suspicion of assisting an offender. They are all currently being held by police.
Police would continue to encourage any witnesses who have not yet spoken to them to do so.
If you can assist, please call Central CID at 101 and reference crime number 54220079230. You can also call CrimeStoppers anonymously at 0800 555111.