Answer:
The metro trains are automated, so there is no driver.
automated
There is so much congestion on the roads that sometimes no cars move at all.
congestion
Explanation:
automated
adjective
1. operated by largely automatic equipment
Example: a fully automated process
congestion
noun
1. a situation in which there is too much traffic and movement is difficult:
The (traffic) congestion in the city gets worse during the summer.
Your mother and I are very proud of you.