As described in the references below, the most complex-equipped ambulance is the ALS equipped ambulance. There are also specialty ambulances for fire, water rescue, mountain rescue, etc. But the basic ambulances are categorized as BLS (Basic Life Support) and ALS.

Johns Hopkins Lifeline / Basic/Advanced Life Support - [ Traduzca esta página ]
... **Advanced Life Support (ALS) ambulances **transport patients who need
a higher level of care during transport. Patients who require ...
www.hopkinslifeline.org/lifesupport.html - 10k - En caché - Páginas similares
Advanced life support (ALS) ambulance shall mean an emergency medical service vehicle that has **complex, specialized, life-sustaining equipment** and, ordinarily, equipped for radio-telephone contact with a physician or hospital. Typical of this type of ambulance would be mobile coronary care units and other ambulance vehicles that are appropriately equipped and staffed by personnel trained and authorized to administer IVs, provide anti-shock trousers, establish and maintain a patient’s airway, defibrillate the heart, relieve pneumothorax conditions and perform other advanced life support procedures or services such as cardiac (EKG) monitoring.
www.killeen.net/Boards&Commissions/Chapter4.pdf