An ambulance was a dedicated vehicle used to transport injured individuals to a hospital.
The newly regenerated Third Doctor was put into an ambulance after he was kidnapped from his hospital room by agents of the Nestene Consciousness. However, he escaped by wheelchair before he could be driven away from Ashbridge Cottage Hospital. (TV: Spearhead from Space)
A guerilla, who had been attacked and knocked unconscious by Ogrons in the grounds of Auderly House, was taken to hospital by ambulance, accompanied by Sergeant Benton. However, when the Third Doctor inadvertently activated the guerilla's time machine back at UNIT H.Q., the man vanished before Benton's eyes. (TV: Day of the Daleks)
An ambulance arrived at the Pharos Project to take the unconscious newly regenerated Fifth Doctor to hospital. The vehicle was subsequently hijacked by Tegan and Nyssa to drive the Doctor to the TARDIS. (TV: Castrovalva)
On 30 December 1999, a severely wounded Seventh Doctor was taken in an ambulance to the Walker General Hospital, after suffering gunshot wounds when he unknowingly walked out of his TARDIS in front of a Chinese-American gang. The bullets were removed, but the surgeons confused his Time Lord biology for human, leading to his death in an ill-fated exploratory surgery. He regenerated several hours afterwards early on 31 December.
Later that evening, Grace Holloway called for an ambulance for the Eighth Doctor, whom she thought insane. Unknown to them, the ambulance was being driven by Chang Lee and the Master was sitting in the back alongside them. The Doctor realised who the Master was when they stopped in a traffic jam. Once both the Doctor and Grace escaped, the Master and Chang Lee used the ambulance to get through the traffic jam. They reached the Institute for Technological Advancement and Research shortly before the Doctor and Grace. (TV: Doctor Who)