The long life of the Ambassador

Like NYC, the fleet of cabs in Calcutta is all painted in yellow. Yet only one brand is allowed, that is the 50 year old...
Like NYC, the fleet of cabs in Calcutta is all painted in yellow. Yet only one brand is allowed, that is the 50 year old Ambassador which is still manufactured. How many decades must have them dealt with traffic ? Luckily, we all know that the main virtue of an Ambassador is patience.