What word describes the traffic when vehicles are totally stopped?
You may be thinking of gridlock
defined by Dictionary.com as:
1. the stoppage of free vehicular movement in an urban area because key intersections are blocked by traffic.
2. the blocking of an intersection by vehicular traffic entering the intersection but unable to pass through it.
Here’s a great picture from timlane.org:
A word that could be used is Standstill
Traffic was so bad it had come to a standstill
Defined by Dictionary.com as:
noun 1. a state of cessation of movement or action; halt; stop: